Create atlas for font rendering

1 files changed, 64 insertions, 0 deletions

diff --git a/font.c b/font.c
index 9198b3a..2a082b3 100644
--- a/font.c
+++ b/font.c
@@ -59,6 +59,70 @@ bool init_freetype(client_state* state, const char* file) {
 		fprintf(stderr, "Failed to set font size\n");
 		return false;
 	}
+	return true;
+}
+
+bool init_atlas(client_state* state) {
+    FT_Int32 load_flags = FT_LOAD_RENDER | FT_LOAD_TARGET_(FT_RENDER_MODE_SDF);
+	for (int i = 32; i < 128; i++) {
+		if (FT_Load_Char(state->ft_face, i, load_flags)) {
+			fprintf(stderr, "Failed to render character %c\n", (char)i);
+		}
+		printf("%c: %u, %u\n", (char)i, state->ft_face->glyph->bitmap.width, state->ft_face->glyph->bitmap.rows);
+		state->atlas.width += state->ft_face->glyph->bitmap.width;
+		state->atlas.height = MAX(state->atlas.height, state->ft_face->glyph->bitmap.rows);
+	}
+
+    glActiveTexture(GL_TEXTURE0);
+    glGenTextures(1, &state->atlas.texture);
+    glBindTexture(GL_TEXTURE_2D, state->atlas.texture);
+
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+
+    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+    glTexImage2D(
+        GL_TEXTURE_2D,
+        0,
+        GL_RED,
+        (GLsizei) state->atlas.width,
+        (GLsizei) state->atlas.height,
+        0,
+        GL_RED,
+        GL_UNSIGNED_BYTE,
+        NULL);
+
+	uint32_t x = 0;
+	for (int i = 32; i < 128; i++) {
+		if (FT_Load_Char(state->ft_face, i, load_flags)) {
+			fprintf(stderr, "Failed to render character %c\n", (char)i);
+		}
+
+        if (FT_Render_Glyph(state->ft_face->glyph, FT_RENDER_MODE_NORMAL)) {
+            fprintf(stderr, "ERROR: could not render glyph of a character with code %d\n", i);
+        }
+
+		state->atlas.metrics[i].advance_x = (float)state->ft_face->glyph->advance.x / 64;
+		state->atlas.metrics[i].advance_y = (float)state->ft_face->glyph->advance.y / 64;
+		state->atlas.metrics[i].bitmap_width = state->ft_face->glyph->bitmap.width;
+		state->atlas.metrics[i].bitmap_height = state->ft_face->glyph->bitmap.rows;
+		state->atlas.metrics[i].texture_offset = x;
+
+        glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+        glTexSubImage2D(
+            GL_TEXTURE_2D,
+            0,
+            x,
+            0,
+            state->ft_face->glyph->bitmap.width,
+            state->ft_face->glyph->bitmap.rows,
+            GL_RED,
+            GL_UNSIGNED_BYTE,
+            state->ft_face->glyph->bitmap.buffer);
+        x += state->ft_face->glyph->bitmap.width;
+	}
 
 	return true;
 }