Fix multi-bg screenshots

src/WallpaperEngine/Application/CWallpaperApplication.cpp

@@ -235,9 +235,10 @@ namespace WallpaperEngine::Application
         glReadPixels (0, 0, width, height, GL_RGB, GL_UNSIGNED_BYTE, buffer);
 
         // build the output file with FreeImage
-        FIBITMAP* bitmap = FreeImage_Allocate (width, height, 24);
+        static FIBITMAP* bitmap = FreeImage_Allocate (width, height, 24);
         RGBQUAD color;
 
+        if (!context.getDriver().requiresSeparateFlips()) {
             // now get access to the pixels
             for (int y = height; y > 0; y--)
             {
@@ -259,6 +260,46 @@ namespace WallpaperEngine::Application
             delete[] buffer;
 
             FreeImage_Unload (bitmap);
+
+            const_cast<CWallpaperApplication*>(&context.getApp())->getContext().settings.screenshot.take = false;
+        } else {
+            const auto RENDERING = context.getDriver().getCurrentlyRendered();
+            static int xoff = 0;
+
+            for (int y = height; y > 0; y--)
+            {
+                for (int x = 0; x < width; x++)
+                {
+                    color.rgbRed = *pixel++;
+                    color.rgbGreen = *pixel++;
+                    color.rgbBlue = *pixel++;
+
+                    // set the pixel in the destination
+                    FreeImage_SetPixelColor (bitmap, x + xoff, (context.getOutput()->renderVFlip() ? (height - y) : y), &color);
+                }
+            }
+
+            for (auto& [name, data] : context.getOutput()->getViewports()) {
+                if (name == RENDERING) {
+                    xoff += data.viewport.z;
+                    break;
+                }
+            }
+
+            const_cast<CWallpaperApplication*>(&context.getApp())->screenshotOutputsDone.push_back(RENDERING);
+
+            if (const_cast<CWallpaperApplication*>(&context.getApp())->screenshotOutputsDone.size() >= context.getOutput()->getViewports().size()) {
+                // finally save the file
+                FreeImage_Save (format, bitmap, filename.c_str (), 0);
+
+                // free all the used memory
+                delete[] buffer;
+
+                FreeImage_Unload (bitmap);
+
+                const_cast<CWallpaperApplication*>(&context.getApp())->getContext().settings.screenshot.take = false;
+            }
+        }
     }
 
     void CWallpaperApplication::show ()
@@ -378,12 +419,13 @@ namespace WallpaperEngine::Application
         // render the scene
         context->render ();
 
-        if (!this->m_context.settings.screenshot.take || videoDriver->getFrameCounter () != 5)
+        if (!this->m_context.settings.screenshot.take || videoDriver->getFrameCounter () < 5)
+            return;
+
+        if (std::find_if(screenshotOutputsDone.begin(), screenshotOutputsDone.end(), [&] (const auto& other) { return other == context->getDriver().getCurrentlyRendered(); }) != screenshotOutputsDone.end())
             return;
 
         this->takeScreenshot (*context, this->m_context.settings.screenshot.path, this->m_context.settings.screenshot.format);
-        // disable screenshot just in case the counter overflows
-        this->m_context.settings.screenshot.take = false;
     }
 
     void CWallpaperApplication::signal (int signal)

src/WallpaperEngine/Application/CWallpaperApplication.h

@@ -123,5 +123,7 @@ namespace WallpaperEngine::Application
         std::unique_ptr<WallpaperEngine::Audio::Drivers::CSDLAudioDriver> audioDriver;
         std::unique_ptr<WallpaperEngine::Render::CRenderContext> context;
         std::unique_ptr<WallpaperEngine::Audio::CAudioContext> audioContext;
+
+        std::vector<std::string> screenshotOutputsDone;
     };
 }

src/WallpaperEngine/Render/Drivers/CVideoDriver.cpp

@@ -21,3 +21,7 @@ bool CVideoDriver::requiresSeparateFlips() const {
 void CVideoDriver::swapOutputBuffer(const std::string& outputName) {
     // intentionally left blank
 }
+
+std::string CVideoDriver::getCurrentlyRendered() const {
+    return "";
+}

src/WallpaperEngine/Render/Drivers/CVideoDriver.h

@@ -69,5 +69,9 @@ namespace WallpaperEngine::Render::Drivers
          * Wayland only: flip output
         */
         virtual void swapOutputBuffer(const std::string& outputName);
+        /**
+         * Wayland only: gets currently rendered output
+        */
+        virtual std::string getCurrentlyRendered() const;
     };
 }

src/WallpaperEngine/Render/Drivers/CWaylandOpenGLDriver.cpp

@@ -500,3 +500,12 @@ void CWaylandOpenGLDriver::swapOutputBuffer(const std::string& outputName) {
         m_frameCounter++;
     }
 }
+
+std::string CWaylandOpenGLDriver::getCurrentlyRendered() const {
+    for (auto& o : m_outputs) {
+        if (o->rendering)
+            return o->name;
+    }
+
+    return "";
+}

src/WallpaperEngine/Render/Drivers/CWaylandOpenGLDriver.h

@@ -80,6 +80,7 @@ namespace WallpaperEngine::Render::Drivers
         bool shouldRenderOutput(const std::string& outputName) const override;
         bool requiresSeparateFlips() const override;
         void swapOutputBuffer(const std::string& outputName) override;
+        std::string getCurrentlyRendered() const override;
 
         GLFWwindow* getWindow ();