From b1d26ed47bfd3725100bde10c20b6ee9b1045e65 Mon Sep 17 00:00:00 2001
From: Alexander Orzechowski <alex@ozal.ski>
Date: Tue, 23 May 2023 02:16:29 -0400
Subject: [PATCH] renderer/gles2: Compute texture coordinates based off of
 vertex positions

---
 include/render/gles2.h           |  2 +-
 render/gles2/renderer.c          | 26 ++++++++++----------------
 render/gles2/shaders/common.vert |  7 ++++---
 3 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/include/render/gles2.h b/include/render/gles2.h
index f54fc835b..e4befc884 100644
--- a/include/render/gles2.h
+++ b/include/render/gles2.h
@@ -25,10 +25,10 @@ struct wlr_gles2_pixel_format {
 struct wlr_gles2_tex_shader {
 	GLuint program;
 	GLint proj;
+	GLint tex_proj;
 	GLint tex;
 	GLint alpha;
 	GLint pos_attrib;
-	GLint tex_attrib;
 };
 
 struct wlr_gles2_renderer {
diff --git a/render/gles2/renderer.c b/render/gles2/renderer.c
index 67168fe94..48883a2fe 100644
--- a/render/gles2/renderer.c
+++ b/render/gles2/renderer.c
@@ -321,27 +321,21 @@ static bool gles2_render_subtexture_with_matrix(
 	glUniform1i(shader->tex, 0);
 	glUniform1f(shader->alpha, alpha);
 
-	const GLfloat x1 = box->x / wlr_texture->width;
-	const GLfloat y1 = box->y / wlr_texture->height;
-	const GLfloat x2 = (box->x + box->width) / wlr_texture->width;
-	const GLfloat y2 = (box->y + box->height) / wlr_texture->height;
-	const GLfloat texcoord[] = {
-		x2, y1, // top right
-		x1, y1, // top left
-		x2, y2, // bottom right
-		x1, y2, // bottom left
-	};
+	float tex_matrix[9];
+	wlr_matrix_identity(tex_matrix);
+	wlr_matrix_translate(tex_matrix, box->x / texture->wlr_texture.width,
+		box->y / texture->wlr_texture.height);
+	wlr_matrix_scale(tex_matrix, box->width / texture->wlr_texture.width,
+		box->height / texture->wlr_texture.height);
+	glUniformMatrix3fv(shader->tex_proj, 1, GL_FALSE, tex_matrix);
 
 	glVertexAttribPointer(shader->pos_attrib, 2, GL_FLOAT, GL_FALSE, 0, verts);
-	glVertexAttribPointer(shader->tex_attrib, 2, GL_FLOAT, GL_FALSE, 0, texcoord);
 
 	glEnableVertexAttribArray(shader->pos_attrib);
-	glEnableVertexAttribArray(shader->tex_attrib);
 
 	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 
 	glDisableVertexAttribArray(shader->pos_attrib);
-	glDisableVertexAttribArray(shader->tex_attrib);
 
 	glBindTexture(texture->target, 0);
 
@@ -828,10 +822,10 @@ struct wlr_renderer *wlr_gles2_renderer_create(struct wlr_egl *egl) {
 		goto error;
 	}
 	renderer->shaders.tex_rgba.proj = glGetUniformLocation(prog, "proj");
+	renderer->shaders.tex_rgba.tex_proj = glGetUniformLocation(prog, "tex_proj");
 	renderer->shaders.tex_rgba.tex = glGetUniformLocation(prog, "tex");
 	renderer->shaders.tex_rgba.alpha = glGetUniformLocation(prog, "alpha");
 	renderer->shaders.tex_rgba.pos_attrib = glGetAttribLocation(prog, "pos");
-	renderer->shaders.tex_rgba.tex_attrib = glGetAttribLocation(prog, "texcoord");
 
 	renderer->shaders.tex_rgbx.program = prog =
 		link_program(renderer, common_vert_src, tex_rgbx_frag_src);
@@ -839,10 +833,10 @@ struct wlr_renderer *wlr_gles2_renderer_create(struct wlr_egl *egl) {
 		goto error;
 	}
 	renderer->shaders.tex_rgbx.proj = glGetUniformLocation(prog, "proj");
+	renderer->shaders.tex_rgbx.tex_proj = glGetUniformLocation(prog, "tex_proj");
 	renderer->shaders.tex_rgbx.tex = glGetUniformLocation(prog, "tex");
 	renderer->shaders.tex_rgbx.alpha = glGetUniformLocation(prog, "alpha");
 	renderer->shaders.tex_rgbx.pos_attrib = glGetAttribLocation(prog, "pos");
-	renderer->shaders.tex_rgbx.tex_attrib = glGetAttribLocation(prog, "texcoord");
 
 	if (renderer->exts.OES_egl_image_external) {
 		renderer->shaders.tex_ext.program = prog =
@@ -851,10 +845,10 @@ struct wlr_renderer *wlr_gles2_renderer_create(struct wlr_egl *egl) {
 			goto error;
 		}
 		renderer->shaders.tex_ext.proj = glGetUniformLocation(prog, "proj");
+		renderer->shaders.tex_ext.tex_proj = glGetUniformLocation(prog, "tex_proj");
 		renderer->shaders.tex_ext.tex = glGetUniformLocation(prog, "tex");
 		renderer->shaders.tex_ext.alpha = glGetUniformLocation(prog, "alpha");
 		renderer->shaders.tex_ext.pos_attrib = glGetAttribLocation(prog, "pos");
-		renderer->shaders.tex_ext.tex_attrib = glGetAttribLocation(prog, "texcoord");
 	}
 
 	pop_gles2_debug(renderer);
diff --git a/render/gles2/shaders/common.vert b/render/gles2/shaders/common.vert
index 4f855a5de..f51548ab3 100644
--- a/render/gles2/shaders/common.vert
+++ b/render/gles2/shaders/common.vert
@@ -1,9 +1,10 @@
 uniform mat3 proj;
+uniform mat3 tex_proj;
 attribute vec2 pos;
-attribute vec2 texcoord;
 varying vec2 v_texcoord;
 
 void main() {
-	gl_Position = vec4(vec3(pos, 1.0) * proj, 1.0);
-	v_texcoord = texcoord;
+	vec3 pos3 = vec3(pos, 1.0);
+	gl_Position = vec4(pos3 * proj, 1.0);
+	v_texcoord = (pos3 * tex_proj).xy;
 }