SDL: Fix mouse emulation with SDL2.

The mouse emulation via keyboard (or other means) was broken with
079037b73990b6107e59c7f1cd971c3a1cc221d1.

2 files changed, 43 insertions, 36 deletions

diff --git a/backends/graphics/surfacesdl/surfacesdl-graphics.cpp b/backends/graphics/surfacesdl/surfacesdl-graphics.cpp
index 7d666bdbfa..b2da47110b 100644
--- a/backends/graphics/surfacesdl/surfacesdl-graphics.cpp
+++ b/backends/graphics/surfacesdl/surfacesdl-graphics.cpp
@@ -32,6 +32,7 @@
 #include "common/textconsole.h"
 #include "common/translation.h"
 #include "common/util.h"
+#include "common/frac.h"
 #ifdef USE_RGB_COLOR
 #include "common/list.h"
 #endif
@@ -125,7 +126,7 @@ SurfaceSdlGraphicsManager::SurfaceSdlGraphicsManager(SdlEventSource *sdlEventSou
 	_hwscreen(0),
 #if SDL_VERSION_ATLEAST(2, 0, 0)
 	_renderer(nullptr), _screenTexture(nullptr),
-	_viewportX(0), _viewportY(0), _renderScaleX(1.0f), _renderScaleY(1.0f), _mouseScaleX(1.0f), _mouseScaleY(1.0f),
+	_viewport(), _windowWidth(1), _windowHeight(1),
 #else
 	_originalBitsPerPixel(0),
 #endif
@@ -890,9 +891,14 @@ bool SurfaceSdlGraphicsManager::loadGFXMode() {
 	SDL_SetColorKey(_osdSurface, SDL_RLEACCEL | SDL_SRCCOLORKEY | SDL_SRCALPHA, kOSDColorKey);
 #endif
 
+#if !SDL_VERSION_ATLEAST(2, 0, 0)
+	// For SDL2 the output resolution might differ from the requested
+	// resolution. We handle resetting the keyboard emulation properly inside
+	// our SDL_SetVideoMode wrapper for SDL2.
 	_eventSource->resetKeyboadEmulation(
 		_videoMode.screenWidth * _videoMode.scaleFactor - 1,
 		effectiveScreenHeight() - 1);
+#endif
 
 	// Distinguish 555 and 565 mode
 	if (_hwscreen->format->Rmask == 0x7C00)
@@ -1774,8 +1780,10 @@ void SurfaceSdlGraphicsManager::warpMouse(int x, int y) {
 		}
 
 #if SDL_VERSION_ATLEAST(2, 0, 0)
-		x1 = (int)((x1 + _viewportX) * _renderScaleX);
-		y1 = (int)((y1 + _viewportY) * _renderScaleY);
+		// Transform our coordinates in "virtual" output coordinate space into
+		// actual output coordinate space.
+		x1 = x1 * _windowWidth  / _videoMode.hardwareWidth;
+		y1 = y1 * _windowHeight / _videoMode.hardwareHeight;
 #endif
 
 		_window->warpMouseInWindow(x1, y1);
@@ -2361,13 +2369,13 @@ void SurfaceSdlGraphicsManager::notifyVideoExpose() {
 
 void SurfaceSdlGraphicsManager::transformMouseCoordinates(Common::Point &point) {
 #if SDL_VERSION_ATLEAST(2, 0, 0)
-	// In fullscreen mode we can easily get coordinates outside the actual
-	// screen area. For example, if black bars are added left/right we can end
-	// up with negative x coordinates if the user moves the mouse inside the
-	// black bar. Here, we post process the received cooridnates to give the
-	// user the feeling the black bars do not exist.
-	point.x = (int)((point.x + _viewportX) * _mouseScaleX);
-	point.y = (int)((point.y + _viewportY) * _mouseScaleY);
+	// In SDL2 the actual output resolution might be different from what we
+	// requested. Thus, we transform the coordinates from actual output
+	// coordinate space into the "virtual" output coordinate space.
+	// Please note that we ignore the possible existence of black bars here,
+	// this avoids the feeling of stickyness to black bars.
+	point.x = point.x * _videoMode.hardwareWidth  / _windowWidth;
+	point.y = point.y * _videoMode.hardwareHeight / _windowHeight;
 #endif
 
 	if (!_overlayVisible) {
@@ -2408,31 +2416,31 @@ SDL_Surface *SurfaceSdlGraphicsManager::SDL_SetVideoMode(int width, int height,
 		return nullptr;
 	}
 
-	// We set the logical renderer size to the requested resolution in
-	// fullscreen. This assures that SDL2 adds black bars if needed to prevent
-	// stretching.
-	if (isFullscreen && SDL_RenderSetLogicalSize(_renderer, width, height) < 0) {
-		deinitializeRenderer();
-		return nullptr;
-	}
+	SDL_GetWindowSize(_window->getSDLWindow(), &_windowWidth, &_windowHeight);
+	// We expect full screen resolution as inputs coming from the event system.
+	_eventSource->resetKeyboadEmulation(_windowWidth - 1, _windowHeight - 1);
+
+	// Calculate the "viewport" for the actual area we draw in. In fullscreen
+	// we can easily get a different resolution than what we requested. In
+	// this case, we add black bars if necessary to assure the aspect ratio
+	// is preserved.
+	const frac_t outputAspect  = intToFrac(_windowWidth) / _windowHeight;
+	const frac_t desiredAspect = intToFrac(width) / height;
 
-	// To provide smooth mouse handling in case black borders are added, we
-	// obtain the actual window size and the internal renderer scaling.
-	// Based on this we calculate scale factors to scale received mouse
-	// coordinates into actual screen area coordinates.
-	SDL_RenderGetScale(_renderer, &_renderScaleX, &_renderScaleY);
-	int windowWidth = 1, windowHeight = 1;
-	SDL_GetWindowSize(_window->getSDLWindow(), &windowWidth, &windowHeight);
+	_viewport.w = _windowWidth;
+	_viewport.h = _windowHeight;
 
-	_mouseScaleX = (width  * _renderScaleX) / windowWidth;
-	_mouseScaleY = (height * _renderScaleY) / windowHeight;
+	// Adjust one dimension for mantaining the aspect ratio.
+	if (abs(outputAspect - desiredAspect) >= (int)(FRAC_ONE / 1000)) {
+		if (outputAspect < desiredAspect) {
+			_viewport.h = height * _windowWidth / width;
+		} else if (outputAspect > desiredAspect) {
+			_viewport.w = width * _windowHeight / height;
+		}
+	}
 
-	// Obtain viewport top left coordinates to transform received coordinates
-	// into visible area coordinates (i.e. including black borders).
-	SDL_Rect viewport;
-	SDL_RenderGetViewport(_renderer, &viewport);
-	_viewportX = viewport.x;
-	_viewportY = viewport.y;
+	_viewport.x = (_windowWidth  - _viewport.w) / 2;
+	_viewport.y = (_windowHeight - _viewport.h) / 2;
 
 	_screenTexture = SDL_CreateTexture(_renderer, SDL_PIXELFORMAT_RGB565, SDL_TEXTUREACCESS_STREAMING, width, height);
 	if (!_screenTexture) {
@@ -2453,7 +2461,7 @@ void SurfaceSdlGraphicsManager::SDL_UpdateRects(SDL_Surface *screen, int numrect
 	SDL_UpdateTexture(_screenTexture, nullptr, screen->pixels, screen->pitch);
 
 	SDL_RenderClear(_renderer);
-	SDL_RenderCopy(_renderer, _screenTexture, NULL, NULL);
+	SDL_RenderCopy(_renderer, _screenTexture, NULL, &_viewport);
 	SDL_RenderPresent(_renderer);
 }
 #endif // SDL_VERSION_ATLEAST(2, 0, 0)
diff --git a/backends/graphics/surfacesdl/surfacesdl-graphics.h b/backends/graphics/surfacesdl/surfacesdl-graphics.h
index 4d74ec575b..ac9844c849 100644
--- a/backends/graphics/surfacesdl/surfacesdl-graphics.h
+++ b/backends/graphics/surfacesdl/surfacesdl-graphics.h
@@ -171,9 +171,8 @@ protected:
 	 * around this API to keep the code paths as close as possible. */
 	SDL_Renderer *_renderer;
 	SDL_Texture *_screenTexture;
-	int _viewportX, _viewportY;
-	float _renderScaleX, _renderScaleY;
-	float _mouseScaleX, _mouseScaleY;
+	SDL_Rect _viewport;
+	int _windowWidth, _windowHeight;
 	void deinitializeRenderer();
 
 	SDL_Surface *SDL_SetVideoMode(int width, int height, int bpp, Uint32 flags);