Implement native visual matching

Implement matching GBM buffer format to EGL NATIVE_VISUAL_ID.
eglChooseConfig cannot match on NATIVE_VISUAL_ID, but GBM/EGL
requires matching formats. Similar logic is implemented in
kmscube code in match_config_to_visual.

X11, Wayland and Null cube demos remain unchanged.

Tested on Raspi-4 and VirtualBox/Ubuntu

kmscube/cube-egl.cpp

@@ -22,7 +22,10 @@ static void print_egl_config(EGLDisplay dpy, EGLConfig cfg)
 	       getconf(EGL_NATIVE_VISUAL_TYPE));
 }
 
-EglState::EglState(void* native_display)
+EglState::EglState(void* native_display) : EglState(native_display, 0) {}
+
+EglState::EglState(void* native_display, EGLint native_visual_id)
+	: m_native_visual_id(native_visual_id)
 {
 	EGLBoolean b;
 	EGLint major, minor, n;
@@ -60,11 +63,11 @@ EglState::EglState(void* native_display)
 	b = eglBindAPI(EGL_OPENGL_ES_API);
 	FAIL_IF(!b, "failed to bind api EGL_OPENGL_ES_API");
 
-	if (s_verbose) {
-		EGLint numConfigs;
-		b = eglGetConfigs(m_display, nullptr, 0, &numConfigs);
-		FAIL_IF(!b, "failed to get number of configs");
+	EGLint numConfigs;
+	b = eglGetConfigs(m_display, nullptr, 0, &numConfigs);
+	FAIL_IF(!b, "failed to get number of configs");
 
+	if (s_verbose) {
 		EGLConfig configs[numConfigs];
 		b = eglGetConfigs(m_display, configs, numConfigs, &numConfigs);
 		FAIL_IF(!b, "failed to get configs");
@@ -75,8 +78,25 @@ EglState::EglState(void* native_display)
 			print_egl_config(m_display, configs[i]);
 	}
 
-	b = eglChooseConfig(m_display, config_attribs, &m_config, 1, &n);
-	FAIL_IF(!b || n != 1, "failed to choose config");
+	std::vector<EGLConfig> configs(numConfigs);
+	b = eglChooseConfig(m_display, config_attribs, configs.data(), numConfigs, &n);
+	FAIL_IF(!b || n < 1, "failed to choose config");
+
+	// elgChooseConfig does implement matching by EGL_NATIVE_VISUAL_ID, do a manual
+	// loop. Picks the first returned if native_visual_id is not set.
+	for (const auto& config : configs) {
+		EGLint id;
+		b = eglGetConfigAttrib(m_display, config, EGL_NATIVE_VISUAL_ID, &id);
+		if (!b) {
+			printf("failed to get native visual id\n");
+			continue;
+		}
+
+		if (id == native_visual_id || !native_visual_id) {
+			m_config = config;
+			break;
+		}
+	}
 
 	if (s_verbose) {
 		printf("Chosen config:\n");

kmscube/cube-egl.h

@@ -6,16 +6,19 @@ class EglState
 {
 public:
 	EglState(void* native_display);
+	EglState(void* native_display, EGLint native_visual_id);
 	~EglState();
 
 	EGLDisplay display() const { return m_display; }
 	EGLConfig config() const { return m_config; }
 	EGLContext context() const { return m_context; }
+	EGLint native_visual_id() const { return m_native_visual_id; }
 
 private:
 	EGLDisplay m_display;
 	EGLConfig m_config;
 	EGLContext m_context;
+	EGLint m_native_visual_id;
 };
 
 class EglSurface

kmscube/cube-gbm.cpp

@@ -49,10 +49,10 @@ class GbmDevice
 class GbmSurface
 {
 public:
-	GbmSurface(GbmDevice& gdev, int width, int height)
+	GbmSurface(GbmDevice& gdev, int width, int height, uint32_t format)
 	{
 		m_surface = gbm_surface_create(gdev.handle(), width, height,
-					       GBM_FORMAT_XRGB8888,
+					       format,
 					       GBM_BO_USE_SCANOUT | GBM_BO_USE_RENDERING);
 		FAIL_IF(!m_surface, "failed to create gbm surface");
 	}
@@ -93,7 +93,7 @@ class GbmEglSurface
 		: card(card), egl(egl), m_width(width), m_height(height),
 		  bo_prev(0), bo_next(0)
 	{
-		gsurface = unique_ptr<GbmSurface>(new GbmSurface(gdev, width, height));
+		gsurface = unique_ptr<GbmSurface>(new GbmSurface(gdev, width, height, egl.native_visual_id()));
 		esurface = eglCreateWindowSurface(egl.display(), egl.config(), gsurface->handle(), NULL);
 		FAIL_IF(esurface == EGL_NO_SURFACE, "failed to create egl surface");
 	}
@@ -319,7 +319,7 @@ void main_gbm()
 	FAIL_IF(!card.has_atomic(), "No atomic modesetting");
 
 	GbmDevice gdev(card);
-	EglState egl(gdev.handle());
+	EglState egl(gdev.handle(), GBM_FORMAT_XRGB8888);
 
 	ResourceManager resman(card);