render/gles2: unify fragment shader

Instead of having 3 different fragment shaders for textures and 1
more for quads, unify them all and compile different variants via
a SOURCE constant.

In the future, we will have more variant dimensions: pre-multiplied
alpha on/off, color transformation, etc. It will become inpractical
to have one file per combination.

Weston has a similar approach:
https://gitlab.freedesktop.org/wayland/weston/-/blob/main/libweston/renderer-gl/fragment.glsl

include/render/gles2.h

@@ -112,6 +112,12 @@ struct wlr_gles2_texture {
 	struct wlr_addon buffer_addon;
 };
 
+enum wlr_gles2_shader_source {
+	WLR_GLES2_SHADER_SOURCE_SINGLE_COLOR = 1,
+	WLR_GLES2_SHADER_SOURCE_TEXTURE_RGBA = 2,
+	WLR_GLES2_SHADER_SOURCE_TEXTURE_RGBX = 3,
+	WLR_GLES2_SHADER_SOURCE_TEXTURE_EXTERNAL = 4,
+};
 
 bool is_gles2_pixel_format_supported(const struct wlr_gles2_renderer *renderer,
 	const struct wlr_gles2_pixel_format *format);

render/gles2/renderer.c

@@ -20,10 +20,7 @@
 #include "types/wlr_matrix.h"
 
 #include "common_vert_src.h"
-#include "quad_frag_src.h"
+#include "common_frag_src.h"
-#include "tex_rgba_frag_src.h"
-#include "tex_rgbx_frag_src.h"
-#include "tex_external_frag_src.h"
 
 static const GLfloat verts[] = {
 	1, 0, // top right
@@ -610,11 +607,11 @@ static void gles2_log(GLenum src, GLenum type, GLuint id, GLenum severity,
 }
 
 static GLuint compile_shader(struct wlr_gles2_renderer *renderer,
-		GLuint type, const GLchar *src) {
+		GLuint type, const GLchar **srcs, size_t srcs_len) {
 	push_gles2_debug(renderer);
 
 	GLuint shader = glCreateShader(type);
-	glShaderSource(shader, 1, &src, NULL);
+	glShaderSource(shader, srcs_len, srcs, NULL);
 	glCompileShader(shader);
 
 	GLint ok;
@@ -630,15 +627,22 @@ static GLuint compile_shader(struct wlr_gles2_renderer *renderer,
 }
 
 static GLuint link_program(struct wlr_gles2_renderer *renderer,
-		const GLchar *vert_src, const GLchar *frag_src) {
+		enum wlr_gles2_shader_source source) {
+	static char frag_preamble[1024];
+	snprintf(frag_preamble, sizeof(frag_preamble),
+		"#define SOURCE %d\n", source);
+
 	push_gles2_debug(renderer);
 
-	GLuint vert = compile_shader(renderer, GL_VERTEX_SHADER, vert_src);
+	const GLchar *vert_src = common_vert_src;
+	GLuint vert = compile_shader(renderer, GL_VERTEX_SHADER, &vert_src, 1);
 	if (!vert) {
 		goto error;
 	}
 
-	GLuint frag = compile_shader(renderer, GL_FRAGMENT_SHADER, frag_src);
+	const GLchar *frag_srcs[2] = { frag_preamble, common_frag_src };
+	GLuint frag =
+		compile_shader(renderer, GL_FRAGMENT_SHADER, frag_srcs, 2);
 	if (!frag) {
 		glDeleteShader(vert);
 		goto error;
@@ -670,6 +674,23 @@ error:
 	return 0;
 }
 
+static bool link_tex_program(struct wlr_gles2_renderer *renderer,
+		struct wlr_gles2_tex_shader *shader,
+		enum wlr_gles2_shader_source source) {
+	shader->program = link_program(renderer, source);
+	if (!shader->program) {
+		return false;
+	}
+
+	shader->proj = glGetUniformLocation(shader->program, "proj");
+	shader->tex = glGetUniformLocation(shader->program, "tex");
+	shader->alpha = glGetUniformLocation(shader->program, "alpha");
+	shader->pos_attrib = glGetAttribLocation(shader->program, "pos");
+	shader->tex_attrib = glGetAttribLocation(shader->program, "texcoord");
+
+	return true;
+}
+
 static bool check_gl_ext(const char *exts, const char *ext) {
 	size_t extlen = strlen(ext);
 	const char *end = exts + strlen(exts);
@@ -824,7 +845,7 @@ struct wlr_renderer *wlr_gles2_renderer_create(struct wlr_egl *egl) {
 
 	GLuint prog;
 	renderer->shaders.quad.program = prog =
-		link_program(renderer, common_vert_src, quad_frag_src);
+		link_program(renderer, WLR_GLES2_SHADER_SOURCE_SINGLE_COLOR);
 	if (!renderer->shaders.quad.program) {
 		goto error;
 	}
@@ -832,39 +853,18 @@ struct wlr_renderer *wlr_gles2_renderer_create(struct wlr_egl *egl) {
 	renderer->shaders.quad.color = glGetUniformLocation(prog, "color");
 	renderer->shaders.quad.pos_attrib = glGetAttribLocation(prog, "pos");
 
-	renderer->shaders.tex_rgba.program = prog =
+	if (!link_tex_program(renderer, &renderer->shaders.tex_rgba,
-		link_program(renderer, common_vert_src, tex_rgba_frag_src);
+			WLR_GLES2_SHADER_SOURCE_TEXTURE_RGBA)) {
-	if (!renderer->shaders.tex_rgba.program) {
 		goto error;
 	}
-	renderer->shaders.tex_rgba.proj = glGetUniformLocation(prog, "proj");
+	if (!link_tex_program(renderer, &renderer->shaders.tex_rgbx,
-	renderer->shaders.tex_rgba.tex = glGetUniformLocation(prog, "tex");
+			WLR_GLES2_SHADER_SOURCE_TEXTURE_RGBX)) {
-	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);
-	if (!renderer->shaders.tex_rgbx.program) {
 		goto error;
 	}
-	renderer->shaders.tex_rgbx.proj = glGetUniformLocation(prog, "proj");
+	if (renderer->exts.OES_egl_image_external &&
-	renderer->shaders.tex_rgbx.tex = glGetUniformLocation(prog, "tex");
+			!link_tex_program(renderer, &renderer->shaders.tex_ext,
-	renderer->shaders.tex_rgbx.alpha = glGetUniformLocation(prog, "alpha");
+			WLR_GLES2_SHADER_SOURCE_TEXTURE_EXTERNAL)) {
-	renderer->shaders.tex_rgbx.pos_attrib = glGetAttribLocation(prog, "pos");
+		goto error;
-	renderer->shaders.tex_rgbx.tex_attrib = glGetAttribLocation(prog, "texcoord");
-
-	if (renderer->exts.OES_egl_image_external) {
-		renderer->shaders.tex_ext.program = prog =
-			link_program(renderer, common_vert_src, tex_external_frag_src);
-		if (!renderer->shaders.tex_ext.program) {
-			goto error;
-		}
-		renderer->shaders.tex_ext.proj = glGetUniformLocation(prog, "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);

render/gles2/shaders/common.frag

@@ -0,0 +1,45 @@
+/* enum wlr_gles2_shader_source */
+#define SOURCE_SINGLE_COLOR 1
+#define SOURCE_TEXTURE_RGBA 2
+#define SOURCE_TEXTURE_RGBX 3
+#define SOURCE_TEXTURE_EXTERNAL 4
+
+#if !defined(SOURCE)
+#error "Missing shader preamble"
+#endif
+
+#if SOURCE == SOURCE_TEXTURE_EXTERNAL
+#extension GL_OES_EGL_image_external : require
+#endif
+
+precision mediump float;
+
+varying vec2 v_texcoord;
+
+#if SOURCE == SOURCE_TEXTURE_EXTERNAL
+uniform samplerExternalOES tex;
+#elif SOURCE == SOURCE_TEXTURE_RGBA || SOURCE == SOURCE_TEXTURE_RGBX
+uniform sampler2D tex;
+#elif SOURCE == SOURCE_SINGLE_COLOR
+uniform vec4 color;
+#endif
+
+#if SOURCE != SOURCE_SINGLE_COLOR
+uniform float alpha;
+#else
+const float alpha = 1.0;
+#endif
+
+vec4 sample_texture() {
+#if SOURCE == SOURCE_TEXTURE_RGBA || SOURCE == SOURCE_TEXTURE_EXTERNAL
+	return texture2D(tex, v_texcoord);
+#elif SOURCE == SOURCE_TEXTURE_RGBX
+	return vec4(texture2D(tex, v_texcoord).rgb, 1.0);
+#elif SOURCE == SOURCE_SINGLE_COLOR
+	return color;
+#endif
+}
+
+void main() {
+	gl_FragColor = sample_texture() * alpha;
+}

render/gles2/shaders/meson.build

@@ -2,10 +2,7 @@ embed = find_program('./embed.sh', native: true)
 
 shaders = [
 	'common.vert',
-	'quad.frag',
+	'common.frag',
-	'tex_rgba.frag',
-	'tex_rgbx.frag',
-	'tex_external.frag',
 ]
 
 foreach name : shaders

render/gles2/shaders/quad.frag

@@ -1,8 +0,0 @@
-precision mediump float;
-varying vec4 v_color;
-varying vec2 v_texcoord;
-uniform vec4 color;
-
-void main() {
-	gl_FragColor = color;
-}

render/gles2/shaders/tex_external.frag

@@ -1,10 +0,0 @@
-#extension GL_OES_EGL_image_external : require
-
-precision mediump float;
-varying vec2 v_texcoord;
-uniform samplerExternalOES texture0;
-uniform float alpha;
-
-void main() {
-	gl_FragColor = texture2D(texture0, v_texcoord) * alpha;
-}

render/gles2/shaders/tex_rgba.frag

@@ -1,8 +0,0 @@
-precision mediump float;
-varying vec2 v_texcoord;
-uniform sampler2D tex;
-uniform float alpha;
-
-void main() {
-	gl_FragColor = texture2D(tex, v_texcoord) * alpha;
-}

render/gles2/shaders/tex_rgbx.frag

@@ -1,8 +0,0 @@
-precision mediump float;
-varying vec2 v_texcoord;
-uniform sampler2D tex;
-uniform float alpha;
-
-void main() {
-	gl_FragColor = vec4(texture2D(tex, v_texcoord).rgb, 1.0) * alpha;
-}