From 2a498a47fc8836eb2baae3a4fb9e7e0316402fa6 Mon Sep 17 00:00:00 2001
From: Leo Tenenbaum <pommicket@gmail.com>
Date: Wed, 25 Nov 2020 14:32:00 -0500
Subject: cutting off text

---
 buffer.c | 19 +++++++++++++------
 main.c   | 16 +++++++++++-----
 text.c   | 40 ++++++++++++++++++++++++++++++++--------
 3 files changed, 56 insertions(+), 19 deletions(-)

diff --git a/buffer.c b/buffer.c
index a1c0516..7fea0d3 100644
--- a/buffer.c
+++ b/buffer.c
@@ -118,15 +118,22 @@ void text_buffer_free(TextBuffer *buffer) {
 }
 
 // Render the text buffer in the given rectangle
-void text_buffer_render(TextBuffer *buffer, Font *font, float box_x, float box_y, float box_w, float box_h) {
+void text_buffer_render(TextBuffer *buffer, Font *font, float x1, float y1, float x2, float y2) {
 	mbstate_t mbstate = {0};
 	uint nblocks = buffer->nblocks;
 	TextBlock *blocks = buffer->blocks;
+	glBegin(GL_LINE_LOOP);
+	glVertex2f(x1,y1);
+	glVertex2f(x1,y2);
+	glVertex2f(x2,y2);
+	glVertex2f(x2,y1);
+	glEnd();
+
 	text_chars_begin(font);
 	TextRenderState text_state = {
-		.x = box_x, .y = box_y,
-		.min_x = box_x, .min_y = box_y,
-		.max_x = box_x+box_w, .max_y = box_y+box_h
+		.x = x1, .y = y1 + text_font_char_height(font),
+		.min_x = x1, .min_y = y1,
+		.max_x = x2, .max_y = y2
 	};
 
 	for (uint block_idx = 0; block_idx < nblocks; ++block_idx) {
@@ -154,8 +161,8 @@ void text_buffer_render(TextBuffer *buffer, Font *font, float box_x, float box_y
 			}
 			switch (c) {
 			case L'\n':
-				text_state.x = box_x;
-				text_state.y -= text_font_char_height(font);
+				text_state.x = x1;
+				text_state.y += text_font_char_height(font);
 				break;
 			case L'\r': break; // for CRLF line endings
 			case L'\t':
diff --git a/main.c b/main.c
index d4c61d9..c655d42 100644
--- a/main.c
+++ b/main.c
@@ -1,3 +1,4 @@
+
 #include "base.h"
 no_warn_start
 #if _WIN32
@@ -96,15 +97,20 @@ int main(void) {
 		glViewport(0, 0, window_width, window_height);
 		glMatrixMode(GL_MODELVIEW);
 		glLoadIdentity();
-		glOrtho(0, window_width, 0, window_height, -1, +1);
+		// pixel coordinates; down is positive y
+		glOrtho(0, window_width, window_height, 0, -1, +1);
 		glClearColor(0, 0, 0, 1);
 		glClear(GL_COLOR_BUFFER_BIT);
 
 		glColor3f(1,1,1);
-		text_buffer_render(&text_buffer, font, 50, window_heightf-50, window_widthf-100, window_heightf-100);
-		if (text_has_err()) {
-			printf("Text error: %s\n", text_get_err());
-			break;
+
+		{
+			float x1 = 50, y1 = 50, x2 = window_widthf-50, y2 = window_heightf-50;
+			text_buffer_render(&text_buffer, font, x1, y1, x2, y2);
+			if (text_has_err()) {
+				printf("Text error: %s\n", text_get_err());
+				break;
+			}
 		}
 
 		//text_buffer_print_debug(&text_buffer);
diff --git a/text.c b/text.c
index ddd7cdc..762bfd9 100644
--- a/text.c
+++ b/text.c
@@ -178,16 +178,40 @@ void text_render_char(Font *font, char32_t c, TextRenderState *state) {
 	stbtt_bakedchar *char_data = font->char_pages[page];
 	if (char_data) { // if page was successfully loaded
 		stbtt_aligned_quad q = {0};
-		// because stb_truetype uses down is positive, we need to negate the y
-		// coordinate, pass it into the function, then negate it back.
-		state->y = -state->y;
 		stbtt_GetBakedQuad(char_data, font->tex_widths[page], font->tex_heights[page],
 			(int)index, &state->x, &state->y, &q, 1);
-		state->y = -state->y;
-		glTexCoord2f(q.s0,q.t1); glVertex2f(q.x0,-q.y1);
-		glTexCoord2f(q.s1,q.t1); glVertex2f(q.x1,-q.y1);
-		glTexCoord2f(q.s1,q.t0); glVertex2f(q.x1,-q.y0);
-		glTexCoord2f(q.s0,q.t0); glVertex2f(q.x0,-q.y0);
+		float s0 = q.s0, t0 = q.t0;
+		float s1 = q.s1, t1 = q.t1;
+		float x0 = q.x0, y0 = q.y0;
+		float x1 = q.x1, y1 = q.y1;
+		float const min_x = state->min_x, max_x = state->max_x;
+		float const min_y = state->min_y, max_y = state->max_y;
+		if (x0 > max_x || y0 > max_y || x1 < min_x || y1 < min_y)
+			return;
+		if (x0 < min_x) {
+			// left side of character is clipped
+			s0 = (min_x-x0) / (x1-x0) * (s1-s0) + s0;
+			x0 = min_x;
+		}
+		if (x1 >= max_x) {
+			// right side of character is clipped
+			s1 = (max_x-x0) / (x1-x0) * (s1-s0) + s0;
+			x1 = max_x;
+		}
+		if (y0 < min_y) {
+			// top side of character is clipped
+			t0 = (min_y-y0) / (y1-y0) * (t1-t0) + t0;
+			y0 = min_y;
+		}
+		if (y1 >= max_y) {
+			// bottom side of character is clipped
+			t1 = (max_y-y0) / (y1-y0) * (t1-t0) + t0;
+			y1 = max_y;
+		}
+		glTexCoord2f(s0,t0); glVertex2f(x0,y0);
+		glTexCoord2f(s0,t1); glVertex2f(x0,y1);
+		glTexCoord2f(s1,t1); glVertex2f(x1,y1);
+		glTexCoord2f(s1,t0); glVertex2f(x1,y0);
 	}
 }
 
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