Added buffer header (with checksum in debug mode)

6 files changed, 801 insertions, 15 deletions

diff --git a/base.h b/base.h
index b4a9b00..c9306a3 100644
--- a/base.h
+++ b/base.h
@@ -48,6 +48,9 @@ typedef int64_t i64;
 typedef unsigned int  uint;
 typedef unsigned long ulong;
 
+typedef long long llong;
+typedef unsigned long long ullong;
+
 #ifdef __GNUC__
 #define WarnUnusedResult __attribute__((warn_unused_result))
 #else
diff --git a/buffer.c b/buffer.c
index e903379..dfa7f11 100644
--- a/buffer.c
+++ b/buffer.c
@@ -161,6 +161,19 @@ BufferPos buffer_end_pos(TextBuffer *buffer) {
 	return (BufferPos){.line = buffer->nlines - 1, .index = buffer->lines[buffer->nlines-1].len};
 }
 
+// Returns a simple checksum of the buffer.
+// This is only used for testing, and shouldn't be relied on.
+static u64 buffer_checksum(TextBuffer *buffer) {
+	u64 sum = 0x40fdd49b58ee4b15; // some random prime number
+	for (Line *line = buffer->lines, *end = line + buffer->nlines; line != end; ++line) {
+		for (char32_t *p = line->str, *p_end = p + line->len; p != p_end; ++p) {
+			sum += *p;
+			sum *= 0xf033ae1b58e6562f; // another random prime number
+			sum += 0x6fcc63c3d38a2bb9; // another random prime number
+		}
+	}
+	return sum;
+}
 
 // Get some number of characters of text from the given position in the buffer.
 // Returns the number of characters gotten.
@@ -660,13 +673,17 @@ static bool buffer_clip_rect(TextBuffer *buffer, float *x1, float *y1, float *x2
 // Render the text buffer in the given rectangle
 // NOTE: also corrects scroll
 void buffer_render(TextBuffer *buffer, float x1, float y1, float x2, float y2) {
-	buffer->x1 = x1; buffer->y1 = y1; buffer->x2 = x2; buffer->y2 = y2;
 	Font *font = buffer->font;
 	u32 nlines = buffer->nlines;
 	Line *lines = buffer->lines;
 	float char_width = text_font_char_width(font),
 		char_height = text_font_char_height(font);
-	glColor3f(0.5f,0.5f,0.5f);
+	float header_height = char_height;
+
+	u32 border_color = 0x7f7f7fff; // color of border around buffer
+
+	// bounding box around buffer & header
+	gl_color_rgba(border_color);
 	glBegin(GL_LINE_STRIP);
 	glVertex2f(x1,y1);
 	glVertex2f(x1,y2);
@@ -675,20 +692,56 @@ void buffer_render(TextBuffer *buffer, float x1, float y1, float x2, float y2) {
 	glVertex2f(x1-1,y1);
 	glEnd();
 
+	TextRenderState text_state = {
+		.x = 0, .y = 0,
+		.min_x = x1, .min_y = y1,
+		.max_x = x2, .max_y = y2
+	};
+
+
+	{ // header
+		glColor3f(1,1,1);
+		float x = x1, y = y1 + char_height * 0.8f;
+		text_render_with_state(font, &text_state, buffer->filename, x, y);
+	#if DEBUG
+		// show checksum
+		char checksum[32] = {0};
+		snprintf(checksum, sizeof checksum - 1, "%08llx", (ullong)buffer_checksum(buffer));
+		gl_color1f(0.5f);
+		float checksum_w = 0;
+		text_get_size(font, checksum, &checksum_w, NULL);
+		x = x2 - checksum_w;
+		text_render_with_state(font, &text_state, checksum, x, y);
+	#endif
+	}
+	
+	y1 += header_height;
+
+	buffer->x1 = x1; buffer->y1 = y1; buffer->x2 = x2; buffer->y2 = y2;
+	// line separating header from buffer proper
+	glBegin(GL_LINES);
+	gl_color_rgba(border_color);
+	glVertex2f(x1, y1);
+	glVertex2f(x2, y1);
+	glEnd();
+
+	
+
 	glColor3f(1,1,1);
 	text_chars_begin(font);
 
+
 	// what x coordinate to start rendering the text from
 	float render_start_x = x1 - (float)buffer->scroll_x * char_width;
 
-	u32 column = 0;
-
-	TextRenderState text_state = {
+	text_state = (TextRenderState){
 		.x = render_start_x, .y = y1 + text_font_char_height(font),
 		.min_x = x1, .min_y = y1,
 		.max_x = x2, .max_y = y2
 	};
 
+	u32 column = 0;
+
 	// @TODO: make this better (we should figure out where to start rendering, etc.)
 	text_state.y -= (float)buffer->scroll_y * char_height;
 
@@ -702,12 +755,12 @@ void buffer_render(TextBuffer *buffer, float x1, float y1, float x2, float y2) {
 			case U'\r': break; // for CRLF line endings
 			case U'\t':
 				do {
-					text_render_char(font, U' ', &text_state);
+					text_render_char(font, &text_state, U' ');
 					++column;
 				} while (column % buffer->tab_width);
 				break;
 			default:
-				text_render_char(font, c, &text_state);
+				text_render_char(font, &text_state, c);
 				++column;
 				break;
 			}
@@ -1354,3 +1407,4 @@ void buffer_redo(TextBuffer *buffer, i64 ntimes) {
 		}
 	}
 }
+
diff --git a/main.c b/main.c
index 2b78b17..790503a 100644
--- a/main.c
+++ b/main.c
@@ -11,6 +11,8 @@ no_warn_end
 #include <wctype.h>
 #include "unicode.h"
 #include "util.c"
+#define MATH_GL
+#include "math.c"
 #include "text.h"
 #include "string32.c"
 #include "arr.c"
diff --git a/math.c b/math.c
new file mode 100644
index 0000000..9ce919c
--- /dev/null
+++ b/math.c
@@ -0,0 +1,718 @@
+#ifdef MATH_GL
+#undef MATH_GL
+#define MATH_GL 1
+#endif
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <assert.h>
+
+#define PIf 3.14159265358979f
+#define HALF_PIf 1.5707963267948966f
+#define TAUf 6.283185307179586f
+#define SQRT2f 1.4142135623730951f
+#define HALF_SQRT2f 0.7071067811865476f
+#define SQRT3f 1.7320508075688772f
+#define HALF_SQRT3f 0.8660254037844386f
+
+#include <math.h>
+
+static float degrees(float r) {
+	return r * (180.0f / PIf);
+}
+static float radians(float r) {
+	return r * (PIf / 180.f);
+}
+
+// map x from the interval [0, 1] to the interval [a, b]. does NOT clamp.
+static float lerpf(float x, float a, float b) {
+	return x * (b-a) + a;
+}
+
+// opposite of lerp; map x from the interval [a, b] to the interval [0, 1]. does NOT clamp.
+static float normf(float x, float a, float b) {
+	return (x-a) / (b-a);
+}
+
+static float clampf(float x, float a, float b) {
+	if (x < a) return a;
+	if (x > b) return b;
+	return x;
+}
+
+static int clampi(int x, int a, int b) {
+	if (x < a) return a;
+	if (x > b) return b;
+	return x;
+}
+
+static i32 clampi32(i32 x, i32 a, i32 b) {
+	if (x < a) return a;
+	if (x > b) return b;
+	return x;
+}
+
+// remap x from the interval [from_a, from_b] to the interval [to_a, to_b], NOT clamping if x is outside the "from" interval.
+static float remapf(float x, float from_a, float from_b, float to_a, float to_b) {
+	float pos = (x - from_a) / (from_b - from_a);
+	return lerpf(pos, to_a, to_b);
+}
+
+static float minf(float a, float b) {
+	return a < b ? a : b;
+}
+
+static float maxf(float a, float b) {
+	return a > b ? a : b;
+}
+
+static float sgnf(float x) {
+	if (x < 0) return -1;
+	if (x > 0) return +1;
+	return 0;
+}
+
+static float smoothstepf(float x) {
+	if (x <= 0) return 0;
+	if (x >= 1) return 1;
+	return x * x * (3 - 2 * x);
+}
+
+static float randf(void) {
+	return (float)rand() / (float)((ulong)RAND_MAX + 1);
+}
+
+static float rand_gauss(void) {
+	// https://en.wikipedia.org/wiki/Normal_distribution#Generating_values_from_normal_distribution
+	float U = randf(), V = randf();
+	return sqrtf(-2 * logf(U)) * cosf(TAUf * V);
+}
+
+static u32 rand_u32(void) {
+	return ((u32)rand() & 0xfff)
+		| ((u32)rand() & 0xfff) << 12
+		| ((u32)rand() & 0xff) << 24;
+}
+
+static float rand_uniform(float from, float to) {
+	return lerpf(randf(), from, to);
+}
+
+static float sigmoidf(float x) {
+	return 1.0f / (1.0f + expf(-x));
+}
+
+// returns ⌈x/y⌉ (x/y rounded up)
+static i32 ceildivi32(i32 x, i32 y) {
+	if (y < 0) {
+		// negating both operands doesn't change the answer
+		x = -x;
+		y = -y;
+	}
+	if (x < 0) {
+		// truncation is the same as ceiling for negative numbers
+		return x / y;
+	} else {
+		return (x + (y-1)) / y;
+	}
+}
+
+typedef struct {
+	float x, y;
+} v2;
+
+static v2 const v2_zero = {0, 0};
+static v2 V2(float x, float y) {
+	v2 v;
+	v.x = x;
+	v.y = y;
+	return v;
+}
+
+static v2 v2_add(v2 a, v2 b) {
+	return V2(a.x + b.x, a.y + b.y);
+}
+
+static v2 v2_add_const(v2 a, float c) {
+	return V2(a.x + c, a.y + c);
+}
+
+static v2 v2_sub(v2 a, v2 b) {
+	return V2(a.x - b.x, a.y - b.y);
+}
+
+static v2 v2_scale(v2 v, float s) {
+	return V2(v.x * s, v.y * s);
+}
+
+static v2 v2_mul(v2 a, v2 b) {
+	return V2(a.x * b.x, a.y * b.y);
+}
+
+static float v2_dot(v2 a, v2 b) {
+	return a.x * b.x + a.y * b.y;
+}
+
+static float v2_len(v2 v) {
+	return sqrtf(v2_dot(v, v));
+}
+
+static v2 v2_lerp(float x, v2 a, v2 b) {
+	return V2(lerpf(x, a.x, b.x), lerpf(x, a.y, b.y));
+}
+
+// rotate v theta radians counterclockwise
+static v2 v2_rotate(v2 v, float theta) {
+	float c = cosf(theta), s = sinf(theta);
+	return V2(
+		c * v.x - s * v.y,
+		s * v.x + c * v.y
+	);
+}
+
+static v2 v2_normalize(v2 v) {
+	float len = v2_len(v);
+	float mul = len == 0.0f ? 1.0f : 1.0f/len;
+	return v2_scale(v, mul);
+}
+
+static float v2_dist(v2 a, v2 b) {
+	return v2_len(v2_sub(a, b));
+}
+
+static float v2_dist_squared(v2 a, v2 b) {
+	v2 diff = v2_sub(a, b);
+	return v2_dot(diff, diff);
+}
+
+static void v2_print(v2 v) {
+	printf("(%f, %f)\n", v.x, v.y);
+}
+
+#if MATH_GL
+static void v2_gl_vertex(v2 v) {
+	glVertex2f(v.x, v.y);
+}
+#endif
+
+static v2 v2_rand_unit(void) {
+	float theta = rand_uniform(0, TAUf);
+	return V2(cosf(theta), sinf(theta));
+}
+
+#if MATH_GL
+static void v2_rand_unit_test(void) {
+	int i;
+	glColor3f(1.0f, 0.0f, 0.0f);
+	glBegin(GL_POINTS);
+	for (i = 0; i < 100000; ++i) {
+		v2_gl_vertex(v2_rand_unit());
+	}
+	glEnd();
+}
+#endif
+
+static v2 v2_polar(float r, float theta) {
+	return V2(r * cosf(theta), r * sinf(theta));
+}
+
+typedef struct {
+	float x, y, z;
+} v3;
+
+static v3 const v3_zero = {0, 0, 0};
+
+static v3 V3(float x, float y, float z) {
+	v3 v;
+	v.x = x;
+	v.y = y;
+	v.z = z;
+	return v;
+}
+
+static v3 v3_from_v2(v2 v) {
+	return V3(v.x, v.y, 0);
+}
+
+#if MATH_GL
+static void v3_gl_vertex(v3 v) {
+	glVertex3f(v.x, v.y, v.z);
+}
+
+static void v3_gl_color(v3 v) {
+	glColor3f(v.x, v.y, v.z);
+}
+
+static void v3_gl_color_alpha(v3 v, float alpha) {
+	glColor4f(v.x, v.y, v.z, alpha);
+}
+#endif
+
+static v3 v3_add(v3 a, v3 b) {
+	return V3(a.x + b.x, a.y + b.y, a.z + b.z);
+}
+
+static v3 v3_sub(v3 a, v3 b) {
+	return V3(a.x - b.x, a.y - b.y, a.z - b.z);
+}
+
+static v3 v3_scale(v3 v, float s) {
+	return V3(v.x * s, v.y * s, v.z * s);
+}
+
+static v3 v3_lerp(float x, v3 a, v3 b) {
+	return V3(lerpf(x, a.x, b.x), lerpf(x, a.y, b.y), lerpf(x, a.z, b.z));
+}
+
+static float v3_dot(v3 u, v3 v) {
+	return u.x*v.x + u.y*v.y + u.z*v.z;
+}
+
+static v3 v3_cross(v3 u, v3 v) {
+	v3 prod = V3(u.y*v.z - u.z*v.y, u.z*v.x - u.x*v.z, u.x*v.y - u.y*v.x);
+	return prod;
+}
+
+static float v3_len(v3 v) {
+	return sqrtf(v3_dot(v, v));
+}
+
+static float v3_dist(v3 a, v3 b) {
+	return v3_len(v3_sub(a, b));
+}
+
+static float v3_dist_squared(v3 a, v3 b) {
+	v3 diff = v3_sub(a, b);
+	return v3_dot(diff, diff);
+}
+
+static v3 v3_normalize(v3 v) {
+	float len = v3_len(v);
+	float mul = len == 0.0f ? 1.0f : 1.0f/len;
+	return v3_scale(v, mul);
+}
+
+static v2 v3_xy(v3 v) {
+	return V2(v.x, v.y);
+}
+
+// a point on a unit sphere 
+static v3 v3_on_sphere(float yaw, float pitch) {
+	return V3(cosf(yaw) * cosf(pitch), sinf(pitch), sinf(yaw) * cosf(pitch));
+}
+
+static void v3_print(v3 v) {
+	printf("(%f, %f, %f)\n", v.x, v.y, v.z);
+}
+
+static v3 v3_rand(void) {
+	return V3(randf(), randf(), randf());
+}
+
+static v3 v3_rand_unit(void) {
+	/*
+		monte carlo method
+		keep generating random points in cube of radius 1 (width 2) centered at origin,
+		until you get a point in the unit sphere, then extend it to find the point lying
+		on the sphere.
+	*/
+	while (1) {
+		v3 v = V3(rand_uniform(-1.0f, +1.0f), rand_uniform(-1.0f, +1.0f), rand_uniform(-1.0f, +1.0f));
+		float dist_squared_to_origin = v3_dot(v, v);
+		if (dist_squared_to_origin <= 1 && dist_squared_to_origin != 0.0f) {
+			return v3_scale(v, 1.0f / sqrtf(dist_squared_to_origin));
+		}
+	}
+	return V3(0, 0, 0);
+}
+
+#if MATH_GL
+static void v3_rand_unit_test(void) {
+	int i;
+	glColor3f(1.0f, 0.0f, 0.0f);
+	glBegin(GL_POINTS);
+	for (i = 0; i < 100000; ++i) {
+		v3_gl_vertex(v3_rand_unit());
+	}
+	glEnd();
+}
+#endif
+
+typedef struct {
+	float x, y, z, w;
+} v4;
+
+static v4 const v4_zero = {0, 0, 0, 0};
+
+static v4 V4(float x, float y, float z, float w) {
+	v4 v;
+	v.x = x;
+	v.y = y;
+	v.z = z;
+	v.w = w;
+	return v;
+}
+
+#if MATH_GL
+static void v4_gl_color(v4 v) {
+	glColor4f(v.x, v.y, v.z, v.w);
+}
+#endif
+
+static v4 v4_add(v4 a, v4 b) {
+	return V4(a.x + b.x, a.y + b.y, a.z + b.z, a.w + b.w);
+}
+
+static v4 v4_sub(v4 a, v4 b) {
+	return V4(a.x - b.x, a.y - b.y, a.z - b.z, a.w - b.w);
+}
+
+static v4 v4_scale(v4 v, float s) {
+	return V4(v.x * s, v.y * s, v.z * s, v.w * s);
+}
+
+static v4 v4_scale_xyz(v4 v, float s) {
+	return V4(v.x * s, v.y * s, v.z * s, v.w);
+}
+
+static v4 v4_lerp(float x, v4 a, v4 b) {
+	return V4(lerpf(x, a.x, b.x), lerpf(x, a.y, b.y), lerpf(x, a.z, b.z), lerpf(x, a.w, b.w));
+}
+
+static float v4_dot(v4 u, v4 v) {
+	return u.x*v.x + u.y*v.y + u.z*v.z + u.w*v.w;
+}
+
+// create a new vector by multiplying the respective components of u and v 
+static v4 v4_mul(v4 u, v4 v) {
+	return V4(u.x * v.x, u.y * v.y, u.z * v.z, u.w * v.w);
+}
+
+static float v4_len(v4 v) {
+	return sqrtf(v4_dot(v, v));
+}
+
+static v4 v4_normalize(v4 v) {
+	float len = v4_len(v);
+	float mul = len == 0.0f ? 1.0f : 1.0f/len;
+	return v4_scale(v, mul);
+}
+
+static v3 v4_xyz(v4 v) {
+	return V3(v.x, v.y, v.z);
+}
+
+static v4 v4_rand(void) {
+	return V4(randf(), randf(), randf(), randf());
+}
+
+static void v4_print(v4 v) {
+	printf("(%f, %f, %f, %f)\n", v.x, v.y, v.z, v.w);
+}
+
+
+// matrices are column-major, because that's what they are in OpenGL 
+typedef struct {
+	float e[16];
+} m4;
+
+static m4 const m4_identity = {{
+	1, 0, 0, 0,
+	0, 1, 0, 0,
+	0, 0, 1, 0,
+	0, 0, 0, 1
+}};
+
+static void m4_print(m4 m) {
+	int i;
+	for (i = 0; i < 4; ++i)
+		printf("[ %f %f %f %f ]\n", m.e[i], m.e[i+4], m.e[i+8], m.e[i+12]);
+	printf("\n");
+}
+
+static m4 M4(
+	float a, float b, float c, float d,
+	float e, float f, float g, float h,
+	float i, float j, float k, float l,
+	float m, float n, float o, float p) {
+	m4 ret;
+	float *x = ret.e;
+	x[0] = a; x[4] = b; x[ 8] = c; x[12] = d;
+	x[1] = e; x[5] = f; x[ 9] = g; x[13] = h;
+	x[2] = i; x[6] = j; x[10] = k; x[14] = l;
+	x[3] = m; x[7] = n; x[11] = o; x[15] = p;
+	return ret;
+}
+
+// see https://en.wikipedia.org/wiki/Rotation_matrix#General_rotations 
+static m4 m4_yaw(float yaw) {
+	float c = cosf(yaw), s = sinf(yaw);
+	return M4(
+		c, 0, -s, 0,
+		0, 1,  0, 0,
+		s, 0,  c, 0,
+		0, 0,  0, 1
+	);
+}
+
+static m4 m4_pitch(float pitch) {
+	float c = cosf(pitch), s = sinf(pitch);
+	return M4(
+		1, 0,  0, 0,
+		0, c, -s, 0,
+		0, s,  c, 0,
+		0, 0,  0, 1
+	);
+}
+
+// https://en.wikipedia.org/wiki/Translation_(geometry) 
+static m4 m4_translate(v3 t) {
+	return M4(
+		1, 0, 0, t.x,
+		0, 1, 0, t.y,
+		0, 0, 1, t.z,
+		0, 0, 0, 1
+	);
+}
+
+// multiply m by [v.x, v.y, v.z, 1] 
+static v3 m4_mul_v3(m4 m, v3 v) {
+	return v3_add(v3_scale(V3(m.e[0], m.e[1], m.e[2]), v.x), v3_add(v3_scale(V3(m.e[4], m.e[5], m.e[6]), v.y),
+		v3_add(v3_scale(V3(m.e[8], m.e[9], m.e[10]), v.z), V3(m.e[12], m.e[13], m.e[14]))));
+}
+
+/*
+4x4 perspective matrix.
+fov - field of view in radians, aspect - width:height aspect ratio, z_near/z_far - clipping planes
+math stolen from gluPerspective (https://www.khronos.org/registry/OpenGL-Refpages/gl2.1/xhtml/gluPerspective.xml)
+*/
+static m4 m4_perspective(float fov, float aspect, float z_near, float z_far) {
+	float f = 1.0f / tanf(fov / 2.0f);
+	return M4(
+		f/aspect, 0, 0, 0,
+		0, f, 0, 0,
+		0, 0, (z_far+z_near) / (z_near-z_far), (2.0f*z_far*z_near) / (z_near-z_far),
+		0, 0, -1, 0
+	);
+}
+
+// windows.h defines near and far, so let's not use those 
+static m4 m4_ortho(float left, float right, float bottom, float top, float near_, float far_) {
+	float tx = -(right + left)/(right - left);
+	float ty = -(top + bottom)/(top - bottom);
+	float tz = -(far_ + near_)/(far_ - near_);
+	return M4(
+		2.0f / (right - left), 0, 0, tx,
+		0, 2.0f / (top - bottom), 0, ty,
+		0, 0, -2.0f / (far_ - near_), tz,
+		0, 0, 0, 1
+	);
+}
+
+
+static m4 m4_mul(m4 a, m4 b) {
+	m4 prod = {0};
+	int i, j;
+	float *x = prod.e;
+	for (i = 0; i < 4; ++i) {
+		for (j = 0; j < 4; ++j, ++x) {
+			float *as = &a.e[j];
+			float *bs = &b.e[4*i];
+			*x = as[0]*bs[0] + as[4]*bs[1] + as[8]*bs[2] + as[12]*bs[3];
+		}
+	}
+	return prod;
+}
+
+static m4 m4_inv(m4 mat) {
+	m4 ret;
+	float *inv = ret.e;
+	float *m = mat.e;
+
+	inv[0] = m[5] * m[10] * m[15] - m[5] * m[11] * m[14] - m[9] * m[6] * m[15] + m[9] * m[7] * m[14] + m[13] * m[6] * m[11] - m[13] * m[7] * m[10];
+	inv[4] = -m[4] * m[10] * m[15] + m[4] * m[11] * m[14] + m[8] * m[6] * m[15] - m[8] * m[7] * m[14] - m[12] * m[6] * m[11] + m[12] * m[7] * m[10];
+	inv[8] = m[4] * m[9] * m[15] - m[4] * m[11] * m[13] - m[8] * m[5] * m[15] + m[8] * m[7] * m[13] + m[12] * m[5] * m[11] - m[12] * m[7] * m[9];
+	inv[12] = -m[4] * m[9] * m[14] + m[4] * m[10] * m[13] + m[8] * m[5] * m[14] - m[8] * m[6] * m[13] - m[12] * m[5] * m[10] + m[12] * m[6] * m[9];
+	inv[1] = -m[1] * m[10] * m[15] + m[1] * m[11] * m[14] + m[9] * m[2] * m[15] - m[9] * m[3] * m[14] - m[13] * m[2] * m[11] + m[13] * m[3] * m[10];
+	inv[5] = m[0] * m[10] * m[15] - m[0] * m[11] * m[14] - m[8] * m[2] * m[15] + m[8] * m[3] * m[14] + m[12] * m[2] * m[11] - m[12] * m[3] * m[10];
+	inv[9] = -m[0] * m[9] * m[15] + m[0] * m[11] * m[13] + m[8] * m[1] * m[15] - m[8] * m[3] * m[13] - m[12] * m[1] * m[11] + m[12] * m[3] * m[9];
+	inv[13] = m[0] * m[9] * m[14] - m[0] * m[10] * m[13] - m[8] * m[1] * m[14] + m[8] * m[2] * m[13] + m[12] * m[1] * m[10] - m[12] * m[2] * m[9];
+	inv[2] = m[1] * m[6] * m[15] - m[1] * m[7] * m[14] - m[5] * m[2] * m[15] + m[5] * m[3] * m[14] + m[13] * m[2] * m[7] - m[13] * m[3] * m[6];
+	inv[6] = -m[0] * m[6] * m[15] + m[0] * m[7] * m[14] + m[4] * m[2] * m[15] - m[4] * m[3] * m[14] - m[12] * m[2] * m[7] + m[12] * m[3] * m[6];
+	inv[10] = m[0] * m[5] * m[15] - m[0] * m[7] * m[13] - m[4] * m[1] * m[15] + m[4] * m[3] * m[13] + m[12] * m[1] * m[7] - m[12] * m[3] * m[5];
+	inv[14] = -m[0] * m[5] * m[14] + m[0] * m[6] * m[13] + m[4] * m[1] * m[14] - m[4] * m[2] * m[13] - m[12] * m[1] * m[6] + m[12] * m[2] * m[5];
+	inv[3] = -m[1] * m[6] * m[11] + m[1] * m[7] * m[10] + m[5] * m[2] * m[11] - m[5] * m[3] * m[10] - m[9] * m[2] * m[7] + m[9] * m[3] * m[6];
+	inv[7] = m[0] * m[6] * m[11] - m[0] * m[7] * m[10] - m[4] * m[2] * m[11] + m[4] * m[3] * m[10] + m[8] * m[2] * m[7] - m[8] * m[3] * m[6];
+	inv[11] = -m[0] * m[5] * m[11] + m[0] * m[7] * m[9] + m[4] * m[1] * m[11] - m[4] * m[3] * m[9] - m[8] * m[1] * m[7] + m[8] * m[3] * m[5];
+	inv[15] = m[0] * m[5] * m[10] - m[0] * m[6] * m[9] - m[4] * m[1] * m[10] + m[4] * m[2] * m[9] + m[8] * m[1] * m[6] - m[8] * m[2] * m[5];
+
+	float det = m[0] * inv[0] + m[1] * inv[4] + m[2] * inv[8] + m[3] * inv[12];
+
+	if (det == 0) {
+		memset(inv, 0, sizeof *inv);
+	} else {
+		det = 1 / det;
+
+		for (int i = 0; i < 16; i++)
+			inv[i] *= det;
+	}
+
+	return ret;
+}
+typedef struct {
+	int x, y;
+} v2i;
+
+static v2i V2I(int x, int y) {
+	v2i v;
+	v.x = x;
+	v.y = y;
+	return v;
+}
+
+static bool rect_contains_point_v2(v2 pos, v2 size, v2 point) {
+	float x1 = pos.x, y1 = pos.y, x2 = pos.x + size.x, y2 = pos.y + size.y,
+		x = point.x, y = point.y;
+	return x >= x1 && x < x2 && y >= y1 && y < y2;
+}
+
+static bool centered_rect_contains_point(v2 center, v2 size, v2 point) {
+	return rect_contains_point_v2(v2_sub(center, v2_scale(size, 0.5f)), size, point);
+}
+
+typedef struct {
+	v2 pos, size;
+} Rect;
+
+static Rect rect(v2 pos, v2 size) {
+	Rect r;
+	r.pos = pos;
+	r.size = size;
+	return r;
+}
+
+static Rect rect4(float x1, float y1, float x2, float y2) {
+	assert(x2 >= x1);
+	assert(y2 >= y1);
+	return rect(V2(x1,y1), V2(x2-x1, y2-y1));
+}
+
+static Rect rect_centered(v2 center, v2 size) {
+	Rect r;
+	r.pos = v2_sub(center, v2_scale(size, 0.5f));
+	r.size = size;
+	return r;
+}
+
+static v2 rect_center(Rect r) {
+	return v2_add(r.pos, v2_scale(r.size, 0.5f));
+}
+
+static bool rect_contains_point(Rect r, v2 point) {
+	return rect_contains_point_v2(r.pos, r.size, point);
+}
+
+static float rect_x1(Rect r) { return r.pos.x; }
+static float rect_y1(Rect r) { return r.pos.y; }
+static float rect_x2(Rect r) { return r.pos.x + r.size.x; }
+static float rect_y2(Rect r) { return r.pos.y + r.size.y; }
+
+static void rect_coords(Rect r, float *x1, float *y1, float *x2, float *y2) {
+	*x1 = r.pos.x;
+	*y1 = r.pos.y;
+	*x2 = r.pos.x + r.size.x;
+	*y2 = r.pos.y + r.size.y;
+}
+
+static void rect_print(Rect r) {
+	printf("Position: (%f, %f), Size: (%f, %f)\n", r.pos.x, r.pos.y, r.size.x, r.size.y);
+}
+
+#if MATH_GL
+// must be rendering GL_QUADS to use these functions! 
+
+static void rect_render(Rect r) {
+	float x1 = r.pos.x, y1 = r.pos.y, x2 = x1 + r.size.x, y2 = y1 + r.size.y;
+	glVertex2f(x1, y1);
+	glVertex2f(x2, y1);
+	glVertex2f(x2, y2);
+	glVertex2f(x1, y2);
+}
+
+static void rect_render_border(Rect r, float border_radius) {
+	float x1 = r.pos.x, y1 = r.pos.y, x2 = x1 + r.size.x, y2 = y1 + r.size.y;
+	//float a = 0.3f; // for debugging
+
+	//glColor4f(1,0,0,a);
+	glVertex2f(x1+border_radius, y1-border_radius);
+	glVertex2f(x1+border_radius, y1+border_radius);
+	glVertex2f(x2+border_radius, y1+border_radius);
+	glVertex2f(x2+border_radius, y1-border_radius);
+	
+	//glColor4f(0,1,0,a);
+	glVertex2f(x1-border_radius, y2-border_radius);
+	glVertex2f(x1-border_radius, y2+border_radius);
+	glVertex2f(x2-border_radius, y2+border_radius);
+	glVertex2f(x2-border_radius, y2-border_radius);
+	
+	//glColor4f(0,0,1,a);
+	glVertex2f(x1-border_radius, y1-border_radius);
+	glVertex2f(x1+border_radius, y1-border_radius);
+	glVertex2f(x1+border_radius, y2-border_radius);
+	glVertex2f(x1-border_radius, y2-border_radius);
+	
+	//glColor4f(1,1,0,a);
+	glVertex2f(x2-border_radius, y1+border_radius);
+	glVertex2f(x2+border_radius, y1+border_radius);
+	glVertex2f(x2+border_radius, y2+border_radius);
+	glVertex2f(x2-border_radius, y2+border_radius);
+}
+
+
+/* 
+	gl grayscale color
+	i am tired of not having this
+*/
+static void gl_color1f(float v) {
+	glColor3f(v,v,v);
+}
+
+/* 
+	gl grayscale+alpha color
+*/
+static void gl_color2f(float v, float a) {
+	glColor4f(v,v,v,a);
+}
+
+// color is 0xRRGGBBAA
+static void gl_color_rgba(u32 color) {
+	glColor4ub((u8)(color >> 24), (u8)(color >> 16), (u8)(color >> 8), (u8)color);
+}
+
+// color is 0xRRGGBB
+static void gl_color_rgb(u32 color) {
+	gl_color_rgba((color << 8) | 0xff);
+}
+
+static void gl_quad(float x1, float y1, float x2, float y2) {
+	glVertex2f(x1, y1);
+	glVertex2f(x2, y1);
+	glVertex2f(x2, y2);
+	glVertex2f(x1, y2);
+}
+
+// returns average of red green and blue components of color
+static float rgba_brightness(u32 color) {
+	u8 r = (u8)(color >> 24), g = (u8)(color >> 16), b = (u8)(color >> 8);
+	return ((float)r+(float)g+(float)b) * (1.0f / 3);
+}
+
+static float rects_intersect(Rect r1, Rect r2) {
+	if (r1.pos.x >= r2.pos.x + r2.size.x) return false; // r1 is to the right of r2
+	if (r2.pos.x >= r1.pos.x + r1.size.x) return false; // r2 is to the right of r1
+	if (r1.pos.y >= r2.pos.y + r2.size.y) return false; // r1 is above r2
+	if (r2.pos.y >= r1.pos.y + r1.size.y) return false; // r2 is above r1
+	return true;
+}
+#endif
+
diff --git a/text.c b/text.c
index 1913bfc..94c4a2c 100644
--- a/text.c
+++ b/text.c
@@ -176,7 +176,7 @@ void text_chars_end(Font *font) {
 	font->curr_page = -1;
 }
 
-void text_render_char(Font *font, char32_t c, TextRenderState *state) {
+void text_render_char(Font *font, TextRenderState *state, char32_t c) {
 	if (c >= 0x30000 && c < 0xE0000){
 		// these Unicode code points are currently unassigned. replace them with a Unicode box.
 		// (specifically, we don't want to use extra memory for pages which
@@ -227,33 +227,40 @@ void text_render_char(Font *font, char32_t c, TextRenderState *state) {
 	}
 }
 
-static void text_render_internal(Font *font, char const *text, float *x, float *y) {
-	mbstate_t mbstate = {0};
-	TextRenderState render_state = {.x = *x, .y = *y, .min_x = -FLT_MAX, .max_x = FLT_MAX, .min_y = -FLT_MAX, .max_y = FLT_MAX};
+void text_render_with_state(Font *font, TextRenderState *render_state, char const *text, float x, float y) {
 	text_chars_begin(font);
+	render_state->x = x;
+	render_state->y = y;
 	char32_t c = 0;
+	mbstate_t mbstate = {0};
 	char const *end = text + strlen(text);
 	while (text != end) {
 		size_t ret = mbrtoc32(&c, text, (size_t)(end - text), &mbstate);
 		if (ret == 0) break;
 		if (ret == (size_t)(-2)) { // incomplete multi-byte character
-			text_render_char(font, '?', &render_state);
+			text_render_char(font, render_state, U'?');
 			text = end; // done reading text
 		} else if (ret == (size_t)(-1)) {
 			// invalid UTF-8; skip this byte
-			text_render_char(font, '?', &render_state);
+			text_render_char(font, render_state, U'?');
 			++text;
 		} else {
 			if (ret != (size_t)(-3))
 				text += ret; // character consists of `ret` bytes
 			switch (c) {
 			default:
-				text_render_char(font, (char32_t)c, &render_state);
+				text_render_char(font, render_state, c);
 				break;
 			}
 		}
 	}
 	text_chars_end(font);
+	
+}
+
+static void text_render_internal(Font *font, char const *text, float *x, float *y) {
+	TextRenderState render_state = {.x = 0, .y = 0, .min_x = -FLT_MAX, .max_x = FLT_MAX, .min_y = -FLT_MAX, .max_y = FLT_MAX};
+	text_render_with_state(font, &render_state, text, *x, *y);
 	*x = render_state.x;
 	*y = render_state.y;
 }
diff --git a/text.h b/text.h
index 25c5e49..820bbd1 100644
--- a/text.h
+++ b/text.h
@@ -32,12 +32,14 @@ extern float text_font_char_width(Font *font);
 extern void text_render(Font *font, char const *text, float x, float y);
 // Get the dimensions of some text.
 extern void text_get_size(Font *font, char const *text, float *width, float *height);
+// Write text, but using a state, starting at (x, y) -- state->x and state->y are ignored. This allows you to control min/max_x/y.
+extern void text_render_with_state(Font *font, TextRenderState *state, char const *text, float x, float y);
 // Begin writing characters.
 extern void text_chars_begin(Font *font);
 // Finish writing characters.
 extern void text_chars_end(Font *font);
 // Render a single character.
-extern void text_render_char(Font *font, char32_t c, TextRenderState *state);
+extern void text_render_char(Font *font, TextRenderState *state, char32_t c);
 // Free memory used by font.
 extern void text_font_free(Font *font);