From 05bf592dec254abdff48e9cc02426efdab77cf5b Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Mon, 29 Jan 2024 01:39:59 -0800
Subject: [PATCH] SDL: Refactor out layer recentering, fix for GB

---
 include/mgba/feature/video-backend.h |  1 +
 src/feature/video-backend.c          | 20 ++++++++++++++++++++
 src/platform/qt/DisplayGL.cpp        | 17 +----------------
 src/platform/sdl/gl-common.c         | 17 +++++------------
 4 files changed, 27 insertions(+), 28 deletions(-)

diff --git a/include/mgba/feature/video-backend.h b/include/mgba/feature/video-backend.h
index 292dc9c82..adf6f8395 100644
--- a/include/mgba/feature/video-backend.h
+++ b/include/mgba/feature/video-backend.h
@@ -74,6 +74,7 @@ struct VideoShader {
 
 void VideoBackendGetFrame(const struct VideoBackend*, struct mRectangle* frame);
 void VideoBackendGetFrameSize(const struct VideoBackend*, unsigned* width, unsigned* height);
+void VideoBackendRecenter(struct VideoBackend* v, unsigned scale);
 
 CXX_GUARD_END
 
diff --git a/src/feature/video-backend.c b/src/feature/video-backend.c
index ae2f0257d..ba13bbe7d 100644
--- a/src/feature/video-backend.c
+++ b/src/feature/video-backend.c
@@ -23,3 +23,23 @@ void VideoBackendGetFrameSize(const struct VideoBackend* v, unsigned* width, uns
 	*width = frame.width;
 	*height = frame.height;
 }
+
+void VideoBackendRecenter(struct VideoBackend* v, unsigned scale) {
+	static const int centeredLayers[] = {VIDEO_LAYER_BACKGROUND, -1};
+	struct mRectangle frame = {0};
+	v->imageSize(v, VIDEO_LAYER_IMAGE, &frame.width, &frame.height);
+	if (scale == 0) {
+		scale = 1;
+	}
+
+	size_t i;
+	for (i = 0; centeredLayers[i] >= 0; ++i) {
+		int width, height;
+		struct mRectangle dims = {0};
+		v->imageSize(v, centeredLayers[i], &width, &height);
+		dims.width = width * scale;
+		dims.height = height * scale;
+		mRectangleCenter(&frame, &dims);
+		v->setLayerDimensions(v, centeredLayers[i], &dims);
+	}
+}
diff --git a/src/platform/qt/DisplayGL.cpp b/src/platform/qt/DisplayGL.cpp
index a1e806ef4..d2de7b9f4 100644
--- a/src/platform/qt/DisplayGL.cpp
+++ b/src/platform/qt/DisplayGL.cpp
@@ -658,22 +658,7 @@ void PainterGL::recenterLayers() {
 	if (!m_context) {
 		return;
 	}
-	const static std::initializer_list<VideoLayer> centeredLayers{VIDEO_LAYER_BACKGROUND};
-	int width, height;
-	mRectangle frame = {0};
-	m_backend->imageSize(m_backend, VIDEO_LAYER_IMAGE, &width, &height);
-	frame.width = width;
-	frame.height = height;
-	unsigned scale = std::max(1U, m_context->videoScale());
-
-	for (VideoLayer l : centeredLayers) {
-		mRectangle dims{};
-		m_backend->imageSize(m_backend, l, &width, &height);
-		dims.width = width * scale;
-		dims.height = height * scale;
-		mRectangleCenter(&frame, &dims);
-		m_backend->setLayerDimensions(m_backend, l, &dims);
-	}
+	VideoBackendRecenter(m_backend, std::max(1U, m_context->videoScale()));
 }
 
 void PainterGL::resize(const QSize& size) {
diff --git a/src/platform/sdl/gl-common.c b/src/platform/sdl/gl-common.c
index 4bd8643b7..1ce9100e8 100644
--- a/src/platform/sdl/gl-common.c
+++ b/src/platform/sdl/gl-common.c
@@ -135,19 +135,11 @@ void mSDLGLCommonRunloop(struct mSDLRenderer* renderer, void* user) {
 
 	if (mSDLGLCommonLoadBackground(v)) {
 		renderer->player.windowUpdated = true;
-
-		struct mRectangle frame;
-		v->layerDimensions(v, VIDEO_LAYER_IMAGE, &frame);
-		int i;
-		for (i = 0; i < VIDEO_LAYER_IMAGE; ++i) {
-			struct mRectangle dims;
-			v->layerDimensions(v, i, &dims);
-			mRectangleCenter(&frame, &dims);
-			v->setLayerDimensions(v, i, &dims);
-		}
-
+		VideoBackendRecenter(v, 1);
 #if SDL_VERSION_ATLEAST(2, 0, 0)
-		SDL_SetWindowSize(renderer->window, frame.width * renderer->ratio, frame.height * renderer->ratio);
+		int width, height;
+		v->imageSize(v, VIDEO_LAYER_IMAGE, &width, &height);
+		SDL_SetWindowSize(renderer->window, width * renderer->ratio, height * renderer->ratio);
 #endif
 	}
 
@@ -175,6 +167,7 @@ void mSDLGLCommonRunloop(struct mSDLRenderer* renderer, void* user) {
 			dims.width = renderer->width;
 			dims.height = renderer->height;
 			v->setLayerDimensions(v, VIDEO_LAYER_IMAGE, &dims);
+			VideoBackendRecenter(v, 1);
 		}
 
 		if (mCoreSyncWaitFrameStart(&context->impl->sync)) {