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/video_core/video_core.cpp

@@ -4,6 +4,7 @@
 
 #include <memory>
 #include "common/logging/log.h"
+#include "core/settings.h"
 #include "video_core/pica.h"
 #include "video_core/renderer_base.h"
 #include "video_core/renderer_opengl/renderer_opengl.h"
@@ -22,6 +23,11 @@ std::atomic<bool> g_hw_shader_enabled;
 std::atomic<bool> g_hw_shader_accurate_gs;
 std::atomic<bool> g_hw_shader_accurate_mul;
 std::atomic<bool> g_renderer_bg_color_update_requested;
+// Screenshot
+std::atomic<bool> g_renderer_screenshot_requested;
+void* g_screenshot_bits;
+std::function<void()> g_screenshot_complete_callback;
+Layout::FramebufferLayout g_screenshot_framebuffer_layout;
 
 /// Initialize the video core
 Core::System::ResultStatus Init(EmuWindow& emu_window) {
@@ -48,4 +54,27 @@ void Shutdown() {
     LOG_DEBUG(Render, "shutdown OK");
 }
 
+void RequestScreenshot(void* data, std::function<void()> callback,
+                       const Layout::FramebufferLayout& layout) {
+    if (g_renderer_screenshot_requested) {
+        LOG_ERROR(Render, "A screenshot is already requested or in progress, ignoring the request");
+        return;
+    }
+    g_screenshot_bits = data;
+    g_screenshot_complete_callback = std::move(callback);
+    g_screenshot_framebuffer_layout = layout;
+    g_renderer_screenshot_requested = true;
+}
+
+u16 GetResolutionScaleFactor() {
+    if (g_hw_renderer_enabled) {
+        return !Settings::values.resolution_factor
+                   ? g_renderer->GetRenderWindow().GetFramebufferLayout().GetScalingRatio()
+                   : Settings::values.resolution_factor;
+    } else {
+        // Software renderer always render at native resolution
+        return 1;
+    }
+}
+
 } // namespace VideoCore