EGL: Add support for EGL_EXT_platform_base

This adds support for EGL_EXT_platform_base and its associated X11 and
Wayland extensions, allowing us to explicitly tell EGL which window
system we are using.

This is based on work by @linkmauve in #1691.

Closes #1691.

README.md

@@ -194,6 +194,7 @@ information on what to include when reporting a bug.
  - [NSGL] Bugfix: `GLFW_COCOA_RETINA_FRAMEBUFFER` had no effect on newer
    macOS versions (#1442)
  - [NSGL] Bugfix: Workaround for swap interval on 10.14 broke on 10.12 (#1483)
+ - [EGL] Added platform selection via the `EGL_EXT_platform_base` extension
 
 
 ## Contact

src/cocoa_window.m

@@ -1721,6 +1721,11 @@ const char* _glfwPlatformGetClipboardString(void)
     } // autoreleasepool
 }
 
+EGLenum _glfwPlatformGetEGLPlatform(void)
+{
+    return 0;
+}
+
 EGLNativeDisplayType _glfwPlatformGetEGLNativeDisplay(void)
 {
     return EGL_DEFAULT_DISPLAY;

src/egl_context.c

@@ -303,6 +303,7 @@ static void destroyContextEGL(_GLFWwindow* window)
 GLFWbool _glfwInitEGL(void)
 {
     int i;
+    const char* extensions;
     const char* sonames[] =
     {
 #if defined(_GLFW_EGL_LIBRARY)
@@ -395,7 +396,39 @@ GLFWbool _glfwInitEGL(void)
         return GLFW_FALSE;
     }
 
+    extensions = eglQueryString(EGL_NO_DISPLAY, EGL_EXTENSIONS);
+    if (extensions && eglGetError() == EGL_SUCCESS)
+        _glfw.egl.EXT_client_extensions = GLFW_TRUE;
+
+    if (_glfw.egl.EXT_client_extensions)
+    {
+        _glfw.egl.EXT_platform_base =
+            _glfwStringInExtensionString("EGL_EXT_platform_base", extensions);
+        _glfw.egl.EXT_platform_x11 =
+            _glfwStringInExtensionString("EGL_EXT_platform_x11", extensions);
+        _glfw.egl.EXT_platform_wayland =
+            _glfwStringInExtensionString("EGL_EXT_platform_wayland", extensions);
+    }
+
+    if (_glfw.egl.EXT_platform_base)
+    {
+        _glfw.egl.GetPlatformDisplayEXT = (PFNEGLGETPLATFORMDISPLAYEXTPROC)
+            eglGetProcAddress("eglGetPlatformDisplayEXT");
+        _glfw.egl.CreatePlatformWindowSurfaceEXT = (PFNEGLCREATEPLATFORMWINDOWSURFACEEXTPROC)
+            eglGetProcAddress("eglCreatePlatformWindowSurfaceEXT");
+    }
+
+    _glfw.egl.platform = _glfwPlatformGetEGLPlatform();
+    if (_glfw.egl.platform)
+    {
+        _glfw.egl.display =
+            eglGetPlatformDisplayEXT(_glfw.egl.platform,
+                                     _glfwPlatformGetEGLNativeDisplay(),
+                                     NULL);
+    }
+    else
         _glfw.egl.display = eglGetDisplay(_glfwPlatformGetEGLNativeDisplay());
+
     if (_glfw.egl.display == EGL_NO_DISPLAY)
     {
         _glfwInputError(GLFW_API_UNAVAILABLE,
@@ -463,6 +496,7 @@ GLFWbool _glfwCreateContextEGL(_GLFWwindow* window,
     EGLint attribs[40];
     EGLConfig config;
     EGLContext share = NULL;
+    EGLNativeWindowType native;
     int index = 0;
 
     if (!_glfw.egl.display)
@@ -598,11 +632,18 @@ GLFWbool _glfwCreateContextEGL(_GLFWwindow* window,
 
     setAttrib(EGL_NONE, EGL_NONE);
 
+    native = _glfwPlatformGetEGLNativeWindow(window);
+    if (_glfw.egl.platform)
+    {
         window->context.egl.surface =
-        eglCreateWindowSurface(_glfw.egl.display,
-                               config,
-                               _glfwPlatformGetEGLNativeWindow(window),
-                               attribs);
+            eglCreatePlatformWindowSurfaceEXT(_glfw.egl.display, config, native, attribs);
+    }
+    else
+    {
+        window->context.egl.surface =
+            eglCreateWindowSurface(_glfw.egl.display, config, native, attribs);
+    }
+
     if (window->context.egl.surface == EGL_NO_SURFACE)
     {
         _glfwInputError(GLFW_PLATFORM_ERROR,

src/egl_context.h

@@ -90,6 +90,8 @@
 #define EGL_CONTEXT_RELEASE_BEHAVIOR_KHR 0x2097
 #define EGL_CONTEXT_RELEASE_BEHAVIOR_NONE_KHR 0
 #define EGL_CONTEXT_RELEASE_BEHAVIOR_FLUSH_KHR 0x2098
+#define EGL_PLATFORM_X11_EXT 0x31d5
+#define EGL_PLATFORM_WAYLAND_EXT 0x31d8
 
 typedef int EGLint;
 typedef unsigned int EGLBoolean;
@@ -136,6 +138,11 @@ typedef GLFWglproc (EGLAPIENTRY * PFN_eglGetProcAddress)(const char*);
 #define eglQueryString _glfw.egl.QueryString
 #define eglGetProcAddress _glfw.egl.GetProcAddress
 
+typedef EGLDisplay (EGLAPIENTRY * PFNEGLGETPLATFORMDISPLAYEXTPROC)(EGLenum,void*,const EGLint*);
+typedef EGLSurface (EGLAPIENTRY * PFNEGLCREATEPLATFORMWINDOWSURFACEEXTPROC)(EGLDisplay,EGLConfig,void*,const EGLint*);
+#define eglGetPlatformDisplayEXT _glfw.egl.GetPlatformDisplayEXT
+#define eglCreatePlatformWindowSurfaceEXT _glfw.egl.CreatePlatformWindowSurfaceEXT
+
 #define _GLFW_EGL_CONTEXT_STATE            _GLFWcontextEGL egl
 #define _GLFW_EGL_LIBRARY_CONTEXT_STATE    _GLFWlibraryEGL egl
 
@@ -156,6 +163,7 @@ typedef struct _GLFWcontextEGL
 //
 typedef struct _GLFWlibraryEGL
 {
+    EGLenum         platform;
     EGLDisplay      display;
     EGLint          major, minor;
     GLFWbool        prefix;
@@ -165,6 +173,10 @@ typedef struct _GLFWlibraryEGL
     GLFWbool        KHR_gl_colorspace;
     GLFWbool        KHR_get_all_proc_addresses;
     GLFWbool        KHR_context_flush_control;
+    GLFWbool        EXT_client_extensions;
+    GLFWbool        EXT_platform_base;
+    GLFWbool        EXT_platform_x11;
+    GLFWbool        EXT_platform_wayland;
 
     void*           handle;
 
@@ -185,6 +197,9 @@ typedef struct _GLFWlibraryEGL
     PFN_eglQueryString          QueryString;
     PFN_eglGetProcAddress       GetProcAddress;
 
+    PFNEGLGETPLATFORMDISPLAYEXTPROC GetPlatformDisplayEXT;
+    PFNEGLCREATEPLATFORMWINDOWSURFACEEXTPROC CreatePlatformWindowSurfaceEXT;
+
 } _GLFWlibraryEGL;
 
 

src/internal.h

@@ -681,6 +681,7 @@ void _glfwPlatformWaitEvents(void);
 void _glfwPlatformWaitEventsTimeout(double timeout);
 void _glfwPlatformPostEmptyEvent(void);
 
+EGLenum _glfwPlatformGetEGLPlatform(void);
 EGLNativeDisplayType _glfwPlatformGetEGLNativeDisplay(void);
 EGLNativeWindowType _glfwPlatformGetEGLNativeWindow(_GLFWwindow* window);
 

src/win32_window.c

@@ -2186,6 +2186,11 @@ const char* _glfwPlatformGetClipboardString(void)
     return _glfw.win32.clipboardString;
 }
 
+EGLenum _glfwPlatformGetEGLPlatform(void)
+{
+    return 0;
+}
+
 EGLNativeDisplayType _glfwPlatformGetEGLNativeDisplay(void)
 {
     return EGL_DEFAULT_DISPLAY;

src/wl_window.c

@@ -1684,6 +1684,14 @@ const char* _glfwPlatformGetClipboardString(void)
     return _glfw.wl.clipboardString;
 }
 
+EGLenum _glfwPlatformGetEGLPlatform(void)
+{
+    if (_glfw.egl.EXT_platform_base && _glfw.egl.EXT_platform_wayland)
+        return EGL_PLATFORM_WAYLAND_EXT;
+    else
+        return 0;
+}
+
 EGLNativeDisplayType _glfwPlatformGetEGLNativeDisplay(void)
 {
     return _glfw.wl.display;

src/x11_window.c

@@ -3048,6 +3048,14 @@ const char* _glfwPlatformGetClipboardString(void)
     return getSelectionString(_glfw.x11.CLIPBOARD);
 }
 
+EGLenum _glfwPlatformGetEGLPlatform(void)
+{
+    if (_glfw.egl.EXT_platform_base && _glfw.egl.EXT_platform_x11)
+        return EGL_PLATFORM_X11_EXT;
+    else
+        return 0;
+}
+
 EGLNativeDisplayType _glfwPlatformGetEGLNativeDisplay(void)
 {
     return _glfw.x11.display;
@@ -3055,6 +3063,9 @@ EGLNativeDisplayType _glfwPlatformGetEGLNativeDisplay(void)
 
 EGLNativeWindowType _glfwPlatformGetEGLNativeWindow(_GLFWwindow* window)
 {
+    if (_glfw.egl.platform)
+        return &window->x11.handle;
+    else
         return (EGLNativeWindowType) window->x11.handle;
 }