Add EGL-based backend for wxGLCanvas

Among other things, this enables wxGLCanvas to be used natively on
Wayland.

Closes https://github.com/wxWidgets/wxWidgets/pull/2038

Closes #17702.

include/wx/unix/glegl.h

@@ -0,0 +1,179 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        wx/unix/glegl.h
+// Purpose:     class common for all EGL-based wxGLCanvas implementations
+// Author:      Scott Talbert
+// Created:     2017-12-26
+// Copyright:   (c) 2017 Scott Talbert <swt@techie.net>
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_UNIX_GLEGL_H_
+#define _WX_UNIX_GLEGL_H_
+
+#include <GL/gl.h>
+
+// This is to avoid including Wayland & EGL headers here to pollute namespace
+struct wl_compositor;
+struct wl_subcompositor;
+struct wl_callback;
+struct wl_egl_window;
+struct wl_surface;
+struct wl_region;
+struct wl_subsurface;
+typedef void *EGLDisplay;
+typedef void *EGLConfig;
+typedef void *EGLSurface;
+typedef void *EGLContext;
+
+class wxGLContextAttrs;
+class wxGLAttributes;
+
+// ----------------------------------------------------------------------------
+// wxGLContext
+// ----------------------------------------------------------------------------
+
+class WXDLLIMPEXP_GL wxGLContext : public wxGLContextBase
+{
+public:
+    wxGLContext(wxGLCanvas *win,
+                const wxGLContext *other = NULL,
+                const wxGLContextAttrs *ctxAttrs = NULL);
+    virtual ~wxGLContext();
+
+    virtual bool SetCurrent(const wxGLCanvas& win) const wxOVERRIDE;
+
+private:
+    EGLContext m_glContext;
+
+    wxDECLARE_CLASS(wxGLContext);
+};
+
+// ----------------------------------------------------------------------------
+// wxGLCanvasEGL
+// ----------------------------------------------------------------------------
+
+class WXDLLIMPEXP_GL wxGLCanvasEGL : public wxGLCanvasBase
+{
+public:
+    // initialization and dtor
+    // -----------------------
+
+    // default ctor doesn't do anything, InitConfig() must be called
+    wxGLCanvasEGL();
+
+    // initializes EGLConfig corresponding to the given attributes
+    bool InitVisual(const wxGLAttributes& dispAttrs);
+
+    // creates EGLSurface
+    bool CreateSurface();
+
+    virtual ~wxGLCanvasEGL();
+
+
+    // implement wxGLCanvasBase methods
+    // --------------------------------
+
+    virtual bool SwapBuffers() wxOVERRIDE;
+
+
+    // X11-specific methods
+    // --------------------
+
+    // get the X11 handle of this window
+    virtual unsigned long GetXWindow() const = 0;
+
+
+    // override some wxWindow methods
+    // ------------------------------
+
+    // return true only if the window is realized: OpenGL context can't be
+    // created until we are
+    virtual bool IsShownOnScreen() const wxOVERRIDE;
+
+
+    // implementation only from now on
+    // -------------------------------
+
+    // get the EGLConfig we use
+    EGLConfig *GetEGLConfig() const { return m_config; }
+    EGLDisplay GetEGLDisplay() const { return m_display; }
+    EGLSurface GetEGLSurface() const { return m_surface; }
+
+    static EGLDisplay GetDisplay();
+
+    // initialize the global default GL config, return false if matching config
+    // not found
+    static bool InitDefaultConfig(const int *attribList);
+
+    // get the default EGL Config (may be NULL, shouldn't be freed by caller)
+    static EGLConfig *GetDefaultConfig() { return ms_glEGLConfig; }
+
+    // free the global GL visual, called by wxGLApp
+    static void FreeDefaultConfig();
+
+    // initializes EGLConfig
+    //
+    // returns NULL if EGLConfig couldn't be initialized, otherwise caller
+    // is responsible for freeing the pointer
+    static EGLConfig *InitConfig(const wxGLAttributes& dispAttrs);
+
+    bool m_readyToDraw;
+    wl_compositor *m_wlCompositor;
+    wl_subcompositor *m_wlSubcompositor;
+    wl_callback *m_wlFrameCallbackHandler;
+    wl_egl_window *m_wlEGLWindow;
+
+private:
+
+    EGLConfig *m_config;
+    EGLDisplay m_display;
+    EGLSurface m_surface;
+
+    unsigned long m_xwindow;
+    wl_surface *m_wlSurface;
+    wl_region *m_wlRegion;
+    wl_subsurface *m_wlSubsurface;
+
+    // the global/default versions of the above
+    static EGLConfig *ms_glEGLConfig;
+};
+
+// ----------------------------------------------------------------------------
+// wxGLApp
+// ----------------------------------------------------------------------------
+
+// this is used in wx/glcanvas.h, prevent it from defining a generic wxGLApp
+#define wxGL_APP_DEFINED
+
+class WXDLLIMPEXP_GL wxGLApp : public wxGLAppBase
+{
+public:
+    wxGLApp() : wxGLAppBase() { }
+
+    // implement wxGLAppBase method
+    virtual bool InitGLVisual(const int *attribList) wxOVERRIDE
+    {
+        return wxGLCanvasEGL::InitDefaultConfig(attribList);
+    }
+
+    // This method is not currently used by the library itself, but remains for
+    // backwards compatibility and also because wxGTK has it we could start
+    // using it for the same purpose in wxX11 too some day.
+    virtual void* GetXVisualInfo() wxOVERRIDE
+    {
+        return wxGLCanvasEGL::GetDefaultConfig();
+    }
+
+    // and override this wxApp method to clean up
+    virtual int OnExit() wxOVERRIDE
+    {
+        wxGLCanvasEGL::FreeDefaultConfig();
+
+        return wxGLAppBase::OnExit();
+    }
+
+private:
+    wxDECLARE_DYNAMIC_CLASS(wxGLApp);
+};
+
+#endif // _WX_UNIX_GLEGL_H_