citra_qt, video_core: Screenshot functionality

Allows capturing screenshot at the current internal resolution (native for software renderer), but a setting is available to capture it in other resolutions. The screenshot is saved to a single PNG in the current layout.

src/citra_qt/bootmanager.cpp

@@ -15,6 +15,7 @@
 #include "input_common/main.h"
 #include "input_common/motion_emu.h"
 #include "network/network.h"
+#include "video_core/video_core.h"
 
 EmuThread::EmuThread(GRenderWindow* render_window) : render_window(render_window) {}
 
@@ -335,6 +336,19 @@ void GRenderWindow::InitRenderTarget() {
     BackupGeometry();
 }
 
+void GRenderWindow::CaptureScreenshot(u16 res_scale, const QString& screenshot_path) {
+    if (!res_scale)
+        res_scale = VideoCore::GetResolutionScaleFactor();
+    const Layout::FramebufferLayout layout{Layout::FrameLayoutFromResolutionScale(res_scale)};
+    screenshot_image = QImage(QSize(layout.width, layout.height), QImage::Format_RGB32);
+    VideoCore::RequestScreenshot(screenshot_image.bits(),
+                                 [=] {
+                                     screenshot_image.mirrored(false, true).save(screenshot_path);
+                                     LOG_INFO(Frontend, "The screenshot is saved.");
+                                 },
+                                 layout);
+}
+
 void GRenderWindow::OnMinimalClientAreaChangeRequest(
     const std::pair<unsigned, unsigned>& minimal_size) {
     setMinimumSize(minimal_size.first, minimal_size.second);