app: confine the eglWindow indirection to the Wayland backend

Only the Wayland backend needs an wl_egl_window between the wl_surface
and EGL. Move code dealing with the indirection to Wayland specific
code.

Then, introduce the eglDriver interface instead of referencing the
native window type directly. This will help when multiple backends are
supported at runtime (e.g. Wayland+X11).

Finally, move the eglDriver implementation methods from GOOS-specific
code to separate EGL-specific files, allowing EGL types to be used
directly instead of unsafe.Pointer and uinptr.

The result is simpler generic EGL code, and easier path towards X11
support.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/egl.go

@@ -15,16 +15,21 @@ import (
 
 type context struct {
 	c             *gl.Functions
-	driver        *window
+	driver        eglDriver
 	eglCtx        *eglContext
-	nwindow       _EGLNativeWindowType
+	eglWin        _EGLNativeWindowType
-	eglWin        *eglWindow
 	eglSurf       _EGLSurface
 	width, height int
 	// For sRGB emulation.
 	srgbFBO *gl.SRGBFBO
 }
 
+type eglDriver interface {
+	eglDisplay() _EGLNativeDisplayType
+	eglWindow(visID int) (_EGLNativeWindowType, int, int, error)
+	eglDestroy()
+}
+
 type eglContext struct {
 	disp     _EGLDisplay
 	config   _EGLConfig
@@ -62,27 +67,28 @@ const (
 func (c *context) Release() {
 	if c.srgbFBO != nil {
 		c.srgbFBO.Release()
+		c.srgbFBO = nil
 	}
 	if c.eglSurf != nilEGLSurface {
 		eglMakeCurrent(c.eglCtx.disp, nilEGLSurface, nilEGLSurface, nilEGLContext)
 		eglDestroySurface(c.eglCtx.disp, c.eglSurf)
 		c.eglSurf = nilEGLSurface
 	}
-	if c.eglWin != nil {
+	c.eglWin = nilEGLNativeWindowType
-		c.eglWin.destroy()
-		c.eglWin = nil
-	}
 	if c.eglCtx != nil {
 		eglDestroyContext(c.eglCtx.disp, c.eglCtx.ctx)
 		eglTerminate(c.eglCtx.disp)
 		eglReleaseThread()
 		c.eglCtx = nil
 	}
-	c.driver = nil
+	if c.driver != nil {
+		c.driver.eglDestroy()
+		c.driver = nil
+	}
 }
 
 func (c *context) Present() error {
-	if c.eglWin == nil {
+	if c.eglWin == nilEGLNativeWindowType {
 		panic("context is not active")
 	}
 	if c.srgbFBO != nil {
@@ -97,13 +103,13 @@ func (c *context) Present() error {
 	return nil
 }
 
-func newContext(w *window) (*context, error) {
+func newContext(d eglDriver) (*context, error) {
-	eglCtx, err := createContext(_EGLNativeDisplayType(w.display()))
+	eglCtx, err := createContext(d.eglDisplay())
 	if err != nil {
 		return nil, err
 	}
 	c := &context{
-		driver: w,
+		driver: d,
 		eglCtx: eglCtx,
 		c:      new(gl.Functions),
 	}
@@ -119,9 +125,11 @@ func (c *context) Lock() {}
 func (c *context) Unlock() {}
 
 func (c *context) MakeCurrent() error {
-	w, width, height := c.driver.nativeWindow(int(c.eglCtx.visualID))
+	win, width, height, err := c.driver.eglWindow(int(c.eglCtx.visualID))
-	win := _EGLNativeWindowType(w)
+	if err != nil {
-	if c.nwindow == win && width == c.width && height == c.height {
+		return err
+	}
+	if c.eglWin == win && width == c.width && height == c.height {
 		return nil
 	}
 	if win == nilEGLNativeWindowType {
@@ -138,29 +146,14 @@ func (c *context) MakeCurrent() error {
 		c.eglSurf = nilEGLSurface
 	}
 	c.width, c.height = width, height
-	c.nwindow = win
+	c.eglWin = win
-	if c.nwindow == nilEGLNativeWindowType {
+	if c.eglWin == nilEGLNativeWindowType {
-		if c.eglWin != nil {
-			c.eglWin.destroy()
-			c.eglWin = nil
-		}
 		return nil
 	}
-	if c.eglWin == nil {
+	eglSurf, err := createSurfaceAndMakeCurrent(c.eglCtx, win)
-		var err error
-		c.eglWin, err = newEGLWindow(win, width, height)
-		if err != nil {
-			return err
-		}
-	} else {
-		c.eglWin.resize(width, height)
-	}
-	eglSurf, err := createSurfaceAndMakeCurrent(c.eglCtx, c.eglWin.window())
 	c.eglSurf = eglSurf
 	if err != nil {
-		c.eglWin.destroy()
+		c.eglWin = nilEGLNativeWindowType
-		c.eglWin = nil
-		c.nwindow = nilEGLNativeWindowType
 		return err
 	}
 	if c.eglCtx.srgb {

app/egl_android.go

@@ -20,3 +20,15 @@ func eglCreateWindowSurface(disp _EGLDisplay, conf _EGLConfig, win _EGLNativeWin
 	eglSurf := C.eglCreateWindowSurface(disp, conf, win, &attribs[0])
 	return eglSurf
 }
+
+func (w *window) eglDestroy() {
+}
+
+func (w *window) eglDisplay() _EGLNativeDisplayType {
+	return nil
+}
+
+func (w *window) eglWindow(visID int) (_EGLNativeWindowType, int, int, error) {
+	win, width, height := w.nativeWindow(visID)
+	return _EGLNativeWindowType(win), width, height, nil
+}

app/egl_wayland.go

@@ -6,7 +6,7 @@ package app
 
 import (
 	"errors"
-	"unsafe"
+	"sync"
 )
 
 /*
@@ -24,29 +24,48 @@ type (
 	_EGLNativeWindowType  = C.EGLNativeWindowType
 )
 
-type eglWindow struct {
+var eglWindows struct {
-	w *C.struct_wl_egl_window
+	mu      sync.Mutex
+	windows map[*C.struct_wl_surface]*C.struct_wl_egl_window
 }
 
-func newEGLWindow(w _EGLNativeWindowType, width, height int) (*eglWindow, error) {
+func (w *window) eglDestroy() {
-	surf := (*C.struct_wl_surface)(unsafe.Pointer(w))
+	surf, _, _ := w.surface()
-	win := C.wl_egl_window_create(surf, C.int(width), C.int(height))
+	if surf == nil {
-	if win == nil {
+		return
-		return nil, errors.New("wl_egl_create_window failed")
+	}
+	eglWindows.mu.Lock()
+	defer eglWindows.mu.Unlock()
+	if eglWin, ok := eglWindows.windows[surf]; ok {
+		C.wl_egl_window_destroy(eglWin)
+		delete(eglWindows.windows, surf)
 	}
-	return &eglWindow{win}, nil
 }
 
-func (w *eglWindow) window() _EGLNativeWindowType {
+func (w *window) eglDisplay() _EGLNativeDisplayType {
-	return w.w
+	return w.display()
 }
 
-func (w *eglWindow) resize(width, height int) {
+func (w *window) eglWindow(visID int) (_EGLNativeWindowType, int, int, error) {
-	C.wl_egl_window_resize(w.w, C.int(width), C.int(height), 0, 0)
+	surf, width, height := w.surface()
-}
+	if surf == nil {
-
+		return nilEGLNativeWindowType, 0, 0, errors.New("wayland: no surface")
-func (w *eglWindow) destroy() {
+	}
-	C.wl_egl_window_destroy(w.w)
+	eglWindows.mu.Lock()
+	defer eglWindows.mu.Unlock()
+	eglWin, ok := eglWindows.windows[surf]
+	if !ok {
+		if eglWindows.windows == nil {
+			eglWindows.windows = make(map[*C.struct_wl_surface]*C.struct_wl_egl_window)
+		}
+		eglWin = C.wl_egl_window_create(surf, C.int(width), C.int(height))
+		if eglWin == nil {
+			return nilEGLNativeWindowType, 0, 0, errors.New("wayland: wl_egl_create_window failed")
+		}
+		eglWindows.windows[surf] = eglWin
+	}
+	C.wl_egl_window_resize(eglWin, C.int(width), C.int(height), 0, 0)
+	return eglWin, width, height, nil
 }
 
 func eglGetDisplay(disp _EGLNativeDisplayType) _EGLDisplay {

app/egl_win.go

@@ -1,20 +0,0 @@
-// SPDX-License-Identifier: Unlicense OR MIT
-
-// +build android windows
-
-package app
-
-type eglWindow struct {
-	w _EGLNativeWindowType
-}
-
-func newEGLWindow(w _EGLNativeWindowType, width, height int) (*eglWindow, error) {
-	return &eglWindow{w}, nil
-}
-
-func (w *eglWindow) window() _EGLNativeWindowType {
-	return w.w
-}
-
-func (w *eglWindow) resize(width, height int) {}
-func (w *eglWindow) destroy()                 {}

app/egl_windows.go

@@ -142,3 +142,15 @@ func eglQueryString(disp _EGLDisplay, name _EGLint) string {
 	r, _, _ := _eglQueryString.Call(uintptr(disp), uintptr(name))
 	return gl.GoString(gl.SliceOf(r))
 }
+
+func (w *window) eglDestroy() {
+}
+
+func (w *window) eglDisplay() _EGLNativeDisplayType {
+	return _EGLNativeDisplayType(w.HDC())
+}
+
+func (w *window) eglWindow(visID int) (_EGLNativeWindowType, int, int, error) {
+	hwnd, width, height := w.HWND()
+	return _EGLNativeWindowType(hwnd), width, height, nil
+}

app/os_android.go

@@ -245,11 +245,7 @@ func (w *window) setStage(stage Stage) {
 	w.event(StageEvent{stage})
 }
 
-func (w *window) display() unsafe.Pointer {
+func (w *window) nativeWindow(visID int) (*C.ANativeWindow, int, int) {
-	return nil
-}
-
-func (w *window) nativeWindow(visID int) (unsafe.Pointer, int, int) {
 	win := w.aNativeWindow()
 	var width, height int
 	if win != nil {
@@ -259,7 +255,7 @@ func (w *window) nativeWindow(visID int) (unsafe.Pointer, int, int) {
 		w, h := C.ANativeWindow_getWidth(win), C.ANativeWindow_getHeight(win)
 		width, height = int(w), int(h)
 	}
-	return unsafe.Pointer(win), width, height
+	return win, width, height
 }
 
 func (w *window) aNativeWindow() *C.ANativeWindow {

app/os_wayland.go

@@ -1036,11 +1036,11 @@ func (w *window) setStage(s Stage) {
 	w.w.event(StageEvent{s})
 }
 
-func (w *window) display() unsafe.Pointer {
+func (w *window) display() *C.struct_wl_display {
-	return unsafe.Pointer(w.disp)
+	return w.disp
 }
 
-func (w *window) nativeWindow(visID int) (unsafe.Pointer, int, int) {
+func (w *window) surface() (*C.struct_wl_surface, int, int) {
 	w.mu.Lock()
 	defer w.mu.Unlock()
 	if w.needAck {
@@ -1052,7 +1052,7 @@ func (w *window) nativeWindow(visID int) (unsafe.Pointer, int, int) {
 		C.wl_surface_set_buffer_scale(w.surf, C.int32_t(scale))
 		w.newScale = false
 	}
-	return unsafe.Pointer(w.surf), width * scale, height * scale
+	return w.surf, width * scale, height * scale
 }
 
 func (w *window) showTextInput(show bool) {}

app/os_windows.go

@@ -430,12 +430,12 @@ func (w *window) destroy() {
 
 func (w *window) showTextInput(show bool) {}
 
-func (w *window) display() uintptr {
+func (w *window) HDC() syscall.Handle {
-	return uintptr(w.hdc)
+	return w.hdc
 }
 
-func (w *window) nativeWindow(visID int) (uintptr, int, int) {
+func (w *window) HWND() (syscall.Handle, int, int) {
-	return uintptr(w.hwnd), w.width, w.height
+	return w.hwnd, w.width, w.height
 }
 
 func convertKeyCode(code uintptr) (rune, bool) {