[gpu] Change GPU acceleration flag from System to Window

* Fixed GPU shader example: enable acceleration by default, and the G
  key to switch the GPU <-> CPU now works
* Avoid crash in SkiaWindowBase::resizeSkiaSurface() when m_glCtx is
  nullptr

examples/hello_laf.cpp

@@ -1,5 +1,5 @@
 // LAF Library
-// Copyright (c) 2019-2022  Igara Studio S.A.
+// Copyright (c) 2019-2024  Igara Studio S.A.
 //
 // This file is released under the terms of the MIT license.
 // Read LICENSE.txt for more information.
@@ -24,7 +24,7 @@ void draw_window(os::Window* window)
   os::draw_text(surface, nullptr, "Hello World", rc.center(),
                 &p, os::TextAlign::Center);
 
-  if (window->isGpuAccelerated())
+  if (window->gpuAcceleration())
     os::draw_text(surface, nullptr, "(GPU)", rc.center()+gfx::Point(0, 24),
                   &p, os::TextAlign::Center);
 
@@ -96,7 +96,7 @@ int app_main(int argc, char* argv[])
             break;
 
           case os::kKeyG:
-            system->setGpuAcceleration(!system->gpuAcceleration());
+            window->setGpuAcceleration(!window->gpuAcceleration());
             // TODO change window backend immediately
             redraw = true;
             break;

examples/shader.cpp

@@ -1,5 +1,5 @@
 // LAF Library
-// Copyright (C) 2022  Igara Studio S.A.
+// Copyright (C) 2022-2024  Igara Studio S.A.
 //
 // This file is released under the terms of the MIT license.
 // Read LICENSE.txt for more information.
@@ -55,6 +55,7 @@ class ShaderWindow {
     m_window = system->makeWindow(256, 256);
     m_window->setCursor(os::NativeCursor::Arrow);
     m_window->setTitle("Shader");
+    m_window->setGpuAcceleration(true);
     repaint();
     m_window->setVisible(true);
   }
@@ -73,8 +74,7 @@ class ShaderWindow {
         if (ev.scancode() == os::kKeyEsc)
           return false;
         else if (ev.scancode() == os::kKeyG) {
-          os::instance()->setGpuAcceleration(
-            !os::instance()->gpuAcceleration());
+          m_window->setGpuAcceleration(!m_window->gpuAcceleration());
         }
         break;
 
@@ -92,7 +92,7 @@ class ShaderWindow {
     SkCanvas* canvas = &static_cast<os::SkiaSurface*>(surface)->canvas();
     skiaPaint(canvas);
 
-    if (m_window->isGpuAccelerated()) {
+    if (m_window->gpuAcceleration()) {
       os::Paint p;
       p.color(gfx::rgba(0, 0, 0));
       os::draw_text(surface, nullptr, "GPU", gfx::Point(12, 12),

os/none/os.cpp

@@ -34,8 +34,6 @@ class NoneSystem : public System {
   Menus* menus() override { return nullptr; }
   NativeDialogs* nativeDialogs() override { return nullptr; }
   EventQueue* eventQueue() override { return nullptr; }
-  bool gpuAcceleration() const override { return false; }
-  void setGpuAcceleration(bool state) override { }
   ScreenRef mainScreen() override { return nullptr; }
   void listScreens(ScreenList& screens) override { }
   Window* defaultWindow() override { return nullptr; }

os/skia/skia_system.h

@@ -42,8 +42,7 @@ namespace os {
 class SkiaSystem final : public SkiaSystemBase {
 public:
   SkiaSystem()
-    : m_defaultWindow(nullptr)
-    , m_gpuAcceleration(false) {
+    : m_defaultWindow(nullptr) {
     SkGraphics::Init();
   }
 
@@ -67,14 +66,6 @@ class SkiaSystem final : public SkiaSystemBase {
       );
   }
 
-  bool gpuAcceleration() const override {
-    return m_gpuAcceleration;
-  }
-
-  void setGpuAcceleration(bool state) override {
-    m_gpuAcceleration = state;
-  }
-
   void setTabletAPI(TabletAPI api) override {
 #if LAF_WINDOWS
     SkiaSystemBase::setTabletAPI(api);
@@ -165,7 +156,6 @@ class SkiaSystem final : public SkiaSystemBase {
 private:
   SkiaWindow* m_defaultWindow;
   Ref<FontManager> m_fontManager;
-  bool m_gpuAcceleration;
   ColorSpaceRef m_windowCS;
 };
 

os/skia/skia_window_base.h

@@ -1,5 +1,5 @@
 // LAF OS Library
-// Copyright (C) 2021-2022  Igara Studio S.A.
+// Copyright (C) 2021-2024  Igara Studio S.A.
 //
 // This file is released under the terms of the MIT license.
 // Read LICENSE.txt for more information.
@@ -82,11 +82,11 @@ class SkiaWindowBase : public T {
 #if SK_SUPPORT_GPU
     // Re-create OpenGL context
     m_gl.detachGL();
-    if (m_glCtx->isValid())
+    if (m_glCtx && m_glCtx->isValid())
       m_glCtx->destroyGLContext();
 
     // GPU-accelerated surface
-    if (os::instance()->gpuAcceleration()) {
+    if (m_glCtx && m_preferGpuAcceleration) {
       m_glCtx->createGLContext();
 
       if (m_glCtx->isValid()) {
@@ -149,15 +149,15 @@ class SkiaWindowBase : public T {
 #if SK_SUPPORT_GPU
     if (m_backend == Backend::NONE ||
         !m_gl.backbufferSurface() ||
-        !m_glCtx->isValid())
+        !m_glCtx ||
+        !m_glCtx->isValid()) {
       return;
+    }
 
     auto surface = static_cast<SkiaSurface*>(this->surface());
     if (!surface)
       return;
 
-    m_glCtx->makeCurrent();
-
     // Draw the small (unscaled) surface to the backbuffer surface
     // scaling it to the this->scale() factor.
     if (m_gl.backbufferSurface() != m_gl.surface()) {
@@ -174,19 +174,26 @@ class SkiaWindowBase : public T {
       dstCanvas->restore();
     }
 
-    surface->flushAndSubmit();
+    m_gl.grCtx()->flushAndSubmit();
     m_glCtx->swapBuffers();
 #endif // SK_SUPPORT_GPU
   }
 
-  bool isGpuAccelerated() const override {
+  bool gpuAcceleration() const override {
 #if SK_SUPPORT_GPU
     return (m_backend == Backend::GL);
 #else
     return false;
 #endif
   }
 
+  void setGpuAcceleration(bool state) override {
+    m_preferGpuAcceleration = state;
+    resetSkiaSurface();
+
+    T::setGpuAcceleration(state);
+  }
+
 #if SK_SUPPORT_GPU
   GrDirectContext* sk_grCtx() const override {
     return m_gl.grCtx();
@@ -232,6 +239,7 @@ class SkiaWindowBase : public T {
 #endif
 
 private:
+  bool m_preferGpuAcceleration = false;
   Backend m_backend = Backend::NONE;
   // Flag used to avoid accessing to an invalid m_surface in the first
   // SkiaWindow::resize() call when the window is created (as the

os/system.h

@@ -146,9 +146,6 @@ namespace os {
     virtual NativeDialogs* nativeDialogs() = 0;
     virtual EventQueue* eventQueue() = 0;
 
-    virtual bool gpuAcceleration() const = 0;
-    virtual void setGpuAcceleration(bool state) = 0;
-
     // Returns the main screen
     virtual ScreenRef mainScreen() = 0;
 

os/window.h

@@ -1,5 +1,5 @@
 // LAF OS Library
-// Copyright (c) 2018-2022  Igara Studio S.A.
+// Copyright (c) 2018-2024  Igara Studio S.A.
 // Copyright (c) 2012-2018  David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -119,7 +119,8 @@ namespace os {
     void invalidate();
 
     // GPU-related functions
-    virtual bool isGpuAccelerated() const = 0;
+    virtual bool gpuAcceleration() const = 0;
+    virtual void setGpuAcceleration(bool state) { }
     virtual void swapBuffers() = 0;
 
     // Focus the window to receive the keyboard input by default.