gl-renderer: fuzzy EGLConfig matching for non-GBM

Implement fuzzy EGLConfig pixel format matching, where we ensure that R, G, B
and A channels have the expected number of bits exactly. This is used on EGL
platforms where the EGLConfig native visual ID is not a DRM format code. On EGL
GBM platform, the old exact matching of native visual ID is kept.

As only the DRM backend uses a DRM format list for picking a config, this patch
should not change any behaviour.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

libweston/renderer-gl/egl-glue.c

@@ -99,27 +99,37 @@ log_egl_config_info(EGLDisplay egldpy, EGLConfig eglconfig)
 		weston_log_continue(" unknown\n");
 }
 
-static int
-match_config_to_visual(EGLDisplay egl_display,
-		       EGLint visual_id,
-		       EGLConfig *configs,
-		       int count)
+static bool
+egl_config_pixel_format_matches(struct gl_renderer *gr,
+				EGLConfig config,
+				const struct pixel_format_info *pinfo)
 {
-	int i;
+	static const EGLint attribs[4] = {
+		EGL_ALPHA_SIZE, EGL_RED_SIZE, EGL_GREEN_SIZE, EGL_BLUE_SIZE
+	};
+	const int *argb[4] = {
+		&pinfo->bits.a, &pinfo->bits.r, &pinfo->bits.g, &pinfo->bits.b
+	};
+	unsigned i;
+	EGLint value;
 
-	for (i = 0; i < count; ++i) {
-		EGLint id;
+	if (gr->platform == EGL_PLATFORM_GBM_KHR) {
+		if (!eglGetConfigAttrib(gr->egl_display, config,
+					EGL_NATIVE_VISUAL_ID, &value))
+			return false;
 
-		if (!eglGetConfigAttrib(egl_display,
-				configs[i], EGL_NATIVE_VISUAL_ID,
-				&id))
-			continue;
-
-		if (id == visual_id)
-			return i;
+		return ((uint32_t)value) == pinfo->format;
 	}
 
-	return -1;
+	for (i = 0; i < 4; i++) {
+		if (!eglGetConfigAttrib(gr->egl_display, config,
+					attribs[i], &value))
+			return false;
+		if (value != *argb[i])
+			return false;
+	}
+
+	return true;
 }
 
 int
@@ -133,6 +143,7 @@ egl_choose_config(struct gl_renderer *gr,
 	EGLint matched = 0;
 	EGLConfig *configs;
 	unsigned i;
+	EGLint j;
 	int config_index = -1;
 
 	if (!eglGetConfigs(gr->egl_display, NULL, 0, &count) || count < 1) {
@@ -153,10 +164,10 @@ egl_choose_config(struct gl_renderer *gr,
 		config_index = 0;
 
 	for (i = 0; config_index == -1 && i < pinfo_count; i++)
-		config_index = match_config_to_visual(gr->egl_display,
-						      pinfo[i]->format,
-						      configs,
-						      matched);
+		for (j = 0; config_index == -1 && j < matched; j++)
+			if (egl_config_pixel_format_matches(gr, configs[j],
+							    pinfo[i]))
+				config_index = j;
 
 	if (config_index != -1)
 		*config_out = configs[config_index];

libweston/renderer-gl/gl-renderer-internal.h

@@ -46,6 +46,7 @@ struct gl_renderer {
 	struct weston_binding *fragment_binding;
 	struct weston_binding *fan_binding;
 
+	EGLenum platform;
 	EGLDisplay egl_display;
 	EGLContext egl_context;
 	EGLConfig egl_config;

libweston/renderer-gl/gl-renderer.c

@@ -3415,6 +3415,7 @@ gl_renderer_display_create(struct weston_compositor *ec,
 	gr->base.surface_get_content_size =
 		gl_renderer_surface_get_content_size;
 	gr->base.surface_copy_content = gl_renderer_surface_copy_content;
+	gr->platform = platform;
 	gr->egl_display = NULL;
 
 	/* extension_suffix is supported */