ONEM-32713 resize surfaces at suspendToTransparent

This is to save the memory allocated for swapchain surfaces
when wpe is going invisible.

Only active with RESIZE_WAYLAND_SURFACES_ON_SUSPEND_PAINTING
compilation var enabled, and with non-composite webgl
disabled.

Author: tomasz-karczewski-red

Source/WebKit/Shared/CoordinatedGraphics/threadedcompositor/ThreadedCompositor.cpp

@@ -169,6 +169,14 @@ void ThreadedCompositor::resume()
         m_scene->setActive(true);
         m_suspendToTransparentState = SuspendToTransparentState::None;
     });
+#if ENABLE(RESIZE_WAYLAND_SURFACES_ON_SUSPEND_PAINTING)
+    if (!m_nonCompositedWebGLEnabled) {
+        // need to resize the view on resume
+        Locker locker { m_attributes.lock };
+        m_attributes.needsResize = true;
+    }
+#endif
+
     m_compositingRunLoop->resume();
     m_compositingRunLoop->scheduleUpdate();
 }
@@ -281,9 +289,20 @@ void ThreadedCompositor::renderLayerTree()
     // GL viewport is updated separately, if necessary. This establishes sequencing where
     // everything inside the will-render and did-render scope is done for a constant-sized scene,
     // and similarly all GL operations are done inside that specific scope.
-
+#if !ENABLE(RESIZE_WAYLAND_SURFACES_ON_SUSPEND_PAINTING)
     if (needsResize)
         m_client.resize(viewportSize);
+#else
+    // since we got this far, we know m_nonCompositedWebGLEnabled is false, no need to check
+    if (needsResize && m_suspendToTransparentState != SuspendToTransparentState::Requested) {
+        m_client.resize(viewportSize);
+    } else if (m_suspendToTransparentState == SuspendToTransparentState::Requested) {
+        // resizing the surfaces, to conserve the memory; going too small (like 1x1) will not properly work
+        // on some platformns, so choosing 16x16 (should only take around 3*1kB in suspended, instead of eg. 3*8MB for HD)
+        constexpr IntSize suspendedSize(16, 16);
+        m_client.resize(suspendedSize);
+    }
+#endif
 
     m_client.willRenderFrame();
 
@@ -301,6 +320,21 @@ void ThreadedCompositor::renderLayerTree()
 
     m_context->swapBuffers();
 
+#if ENABLE(RESIZE_WAYLAND_SURFACES_ON_SUSPEND_PAINTING)
+    // since we got this far, we know m_nonCompositedWebGLEnabled is false, no need to check
+    if (m_suspendToTransparentState == SuspendToTransparentState::WaitingForFrameComplete) {
+        /*  With triple buffering we normally have 3 screen buffers. The backing surfaces may only be really
+            resized when they're presented - so we need 3 buffer swaps to make sure all these surfaces
+            are resized to the requested suspendedSize, thus saving the memory in suspend
+            (one swapBuffers is already done above) */
+        for (int i=0; i<2; ++i) {
+            glClearColor(0, 0, 0, 0);
+            glClear(GL_COLOR_BUFFER_BIT);
+            m_context->swapBuffers();
+        }
+    }
+#endif
+
     if (m_scene->isActive())
         m_client.didRenderFrame();
 }

Source/cmake/OptionsWPE.cmake

@@ -107,6 +107,7 @@ WEBKIT_OPTION_DEFINE(USE_EXTERNAL_HOLEPUNCH "Whether to enable external holepunc
 WEBKIT_OPTION_DEFINE(ENABLE_ACCELERATED_2D_CANVAS "Whether to enable accelerated 2D canvas" PRIVATE OFF)
 WEBKIT_OPTION_DEFINE(ENABLE_OIPF_VK "Whether to enable OIPF keys for DAE applications" PRIVATE OFF)
 WEBKIT_OPTION_DEFINE(USE_LINUX_FTRACE "Whether to use ftrace based webkit tracing" PRIVATE OFF)
+WEBKIT_OPTION_DEFINE(ENABLE_RESIZE_WAYLAND_SURFACES_ON_SUSPEND_PAINTING "Whether to enable resizing of wayland surfaces when painting is suspended" PRIVATE OFF)
 
 # Supported platforms.
 WEBKIT_OPTION_DEFINE(USE_WPEWEBKIT_PLATFORM_WESTEROS "Whether to enable support for the Westeros platform" PUBLIC OFF)
@@ -441,4 +442,4 @@ if (USE_LIBBACKTRACE)
     set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE}${CMAKE_COMPILER_SIZE_OPT_FLAGS} -funwind-tables")
 
     set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG}${CMAKE_COMPILER_SIZE_OPT_FLAGS} -funwind-tables")
-endif ()
+endif ()