From dd5bc398169028c8b0fbc1d1d0084fbac417b256 Mon Sep 17 00:00:00 2001
From: Gleb Mazovetskiy <glex.spb@gmail.com>
Date: Sun, 13 Oct 2019 12:50:16 +0100
Subject: [PATCH] Get a fresh window surface before rendering to it (#358)

* Get a fresh window surface before rendering to it

It is possible that a window surface gets invalidated since we initially
obtained it. We need to call GetWindowSurface every time we want one,
instead of keeping a pointer to a possibly stale one.

See https://hg.libsdl.org/SDL/file/369b01006eb2/src/video/SDL_video.c#l2312

Fixes #351
---
 CMakeLists.txt            |  1 +
 SourceX/dx.cpp            | 19 ++++++++-----------
 SourceX/miniwin/ddraw.cpp | 17 +++++++++++++++++
 SourceX/miniwin/ddraw.h   |  7 ++++++-
 SourceX/storm/storm.cpp   |  4 ++--
 5 files changed, 34 insertions(+), 14 deletions(-)
 create mode 100644 SourceX/miniwin/ddraw.cpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f55278d79..fa9f7412a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -205,6 +205,7 @@ add_library(devilution STATIC
 
 set(devilutionx_SRCS
   SourceX/dx.cpp
+  SourceX/miniwin/ddraw.cpp
   SourceX/miniwin/misc.cpp
   SourceX/miniwin/misc_io.cpp
   SourceX/miniwin/misc_msg.cpp
diff --git a/SourceX/dx.cpp b/SourceX/dx.cpp
index b35975de0..0f8c935ff 100644
--- a/SourceX/dx.cpp
+++ b/SourceX/dx.cpp
@@ -22,8 +22,8 @@ SDL_Texture *texture;
 SDL_Palette *palette;
 unsigned int pal_surface_palette_version = 0;
 
-/** 32-bit in-memory backbuffer surface */
-SDL_Surface *surface;
+/** 24-bit renderer texture surface */
+SDL_Surface *renderer_texture_surface = nullptr;
 
 /** 8-bit surface wrapper around #gpBuffer */
 SDL_Surface *pal_surface;
@@ -58,9 +58,7 @@ void dx_create_back_buffer()
 
 void dx_create_primary_surface()
 {
-#ifdef USE_SDL1
-	surface = SDL_GetVideoSurface();
-#else
+#ifndef USE_SDL1
 	if (renderer) {
 		int width, height;
 		if (SDL_GetRendererOutputSize(renderer, &width, &height) <= -1) {
@@ -69,12 +67,10 @@ void dx_create_primary_surface()
 		Uint32 format;
 		if (SDL_QueryTexture(texture, &format, nullptr, nullptr, nullptr) < 0)
 			ErrSdl();
-		surface = SDL_CreateRGBSurfaceWithFormat(0, width, height, SDL_BITSPERPIXEL(format), format);
-	} else {
-		surface = SDL_GetWindowSurface(window);
+		renderer_texture_surface = SDL_CreateRGBSurfaceWithFormat(0, width, height, SDL_BITSPERPIXEL(format), format);
 	}
 #endif
-	if (surface == NULL) {
+	if (GetOutputSurface() == nullptr) {
 		ErrSdl();
 	}
 }
@@ -140,7 +136,7 @@ void dx_cleanup()
 	SDL_FreeSurface(pal_surface);
 	pal_surface = nullptr;
 	SDL_FreePalette(palette);
-	SDL_FreeSurface(surface);
+	SDL_FreeSurface(renderer_texture_surface);
 	SDL_DestroyTexture(texture);
 	SDL_DestroyRenderer(renderer);
 	SDL_DestroyWindow(window);
@@ -195,7 +191,7 @@ void BltFast(DWORD dwX, DWORD dwY, LPRECT lpSrcRect)
 	};
 
 	// Convert from 8-bit to 32-bit
-	if (SDL_BlitSurface(pal_surface, &src_rect, surface, &dst_rect) <= -1) {
+	if (SDL_BlitSurface(pal_surface, &src_rect, GetOutputSurface(), &dst_rect) <= -1) {
 		ErrSdl();
 	}
 
@@ -204,6 +200,7 @@ void BltFast(DWORD dwX, DWORD dwY, LPRECT lpSrcRect)
 
 void RenderPresent()
 {
+	SDL_Surface *surface = GetOutputSurface();
 	assert(!SDL_MUSTLOCK(surface));
 
 	if (!bufferUpdated) {
diff --git a/SourceX/miniwin/ddraw.cpp b/SourceX/miniwin/ddraw.cpp
new file mode 100644
index 000000000..fc9a3774e
--- /dev/null
+++ b/SourceX/miniwin/ddraw.cpp
@@ -0,0 +1,17 @@
+#include "miniwin/ddraw.h"
+
+namespace dvl {
+
+extern SDL_Surface *renderer_texture_surface; // defined in dx.cpp
+
+SDL_Surface *GetOutputSurface() {
+#ifdef USE_SDL1
+	return SDL_GetVideoSurface();
+#else
+	if (renderer)
+		return renderer_texture_surface;
+	return SDL_GetWindowSurface(window);
+#endif
+}
+
+} // namespace dvl
diff --git a/SourceX/miniwin/ddraw.h b/SourceX/miniwin/ddraw.h
index 9c2d4997c..fb335cda7 100644
--- a/SourceX/miniwin/ddraw.h
+++ b/SourceX/miniwin/ddraw.h
@@ -7,10 +7,15 @@ extern SDL_Window *window;
 extern SDL_Renderer *renderer;
 extern SDL_Texture *texture;
 
-extern SDL_Surface *surface;
 extern SDL_Palette *palette;
 extern SDL_Surface *pal_surface;
 extern unsigned int pal_surface_palette_version;
 extern bool bufferUpdated;
 
+// Returns:
+// SDL1: Video surface.
+// SDL2, no upscale: Window surface.
+// SDL2, upscale: Renderer texture surface.
+SDL_Surface *GetOutputSurface();
+
 } // namespace dvl
diff --git a/SourceX/storm/storm.cpp b/SourceX/storm/storm.cpp
index b1d71d1d4..b32ed172c 100644
--- a/SourceX/storm/storm.cpp
+++ b/SourceX/storm/storm.cpp
@@ -684,7 +684,7 @@ BOOL SVidPlayContinue(void)
 
 #ifndef USE_SDL1
 	if (renderer) {
-		if (SDL_BlitSurface(SVidSurface, NULL, surface, NULL) <= -1) {
+		if (SDL_BlitSurface(SVidSurface, NULL, GetOutputSurface(), NULL) <= -1) {
 			SDL_Log(SDL_GetError());
 			return false;
 		}
@@ -716,7 +716,7 @@ BOOL SVidPlayContinue(void)
 		Uint32 format = SDL_GetWindowPixelFormat(window);
 		SDL_Surface *tmp = SDL_ConvertSurfaceFormat(SVidSurface, format, 0);
 #endif
-		if (SDL_BlitScaled(tmp, NULL, surface, &pal_surface_offset) <= -1) {
+		if (SDL_BlitScaled(tmp, NULL, GetOutputSurface(), &pal_surface_offset) <= -1) {
 			SDL_Log(SDL_GetError());
 			return false;
 		}