Refactor refreshrate handling from int to float.

With SDL 2 the refreshrate handling was rather limited by SDL 2 only
supporting integer refreshrates, making it impossible to represent the
common 59.95hz and other non-integer refreshrates. Quake II works around
this by assuming a refreshrate of 2hz higher than returned by SDL.

SDL 3 finally supports float refreshrates. Refactor the internal API to
also use floats.

This should be a no-op since the 'refreshrate * 1.02' logic stayes in
place for the time being. This can be reevaluated at a later time for
the SDL 3 build, but needs testing.

As a nice side effect fix the `vid_displayrefreshrate` cvar. It was
broken in both SDL 2 and 3 since it was always overwritten with the
actual display refresh rate.

src/client/input/sdl2.c

@@ -701,7 +701,7 @@ IN_Update(void)
 				{
 					// make sure GLimp_GetRefreshRate() will query from SDL again - the window might
 					// be on another display now!
-					glimp_refreshRate = -1;
+					glimp_refreshRate = -1.0f;
 				}
 				else if (event.window.event == SDL_WINDOWEVENT_SHOWN)
 				{

src/client/input/sdl3.c

@@ -701,7 +701,7 @@ IN_Update(void)
 				{
 					// make sure GLimp_GetRefreshRate() will query from SDL again - the window might
 					// be on another display now!
-					glimp_refreshRate = -1;
+					glimp_refreshRate = -1.0;
 				}
 				else if (event.window.event == SDL_WINDOWEVENT_SHOWN)
 				{

src/client/refresh/gl3/gl3_sdl.c

@@ -27,7 +27,6 @@
  * =======================================================================
  */
 
-#include "SDL3/SDL_video.h"
 #include "header/local.h"
 
 #ifdef USE_SDL3

src/client/vid/glimp_sdl2.c

@@ -33,7 +33,7 @@
 #include <SDL2/SDL.h>
 #include <SDL2/SDL_video.h>
 
-int glimp_refreshRate = -1;
+float glimp_refreshRate = -1.0f;
 
 static cvar_t *vid_displayrefreshrate;
 static cvar_t *vid_displayindex;
@@ -733,35 +733,19 @@ GLimp_GrabInput(qboolean grab)
 }
 
 /*
- * Returns the current display refresh rate. There're 2 limitations:
- *
- * * The timing code in frame.c only understands full integers, so
- *   values given by vid_displayrefreshrate are always round up. For
- *   example 59.95 become 60. Rounding up is the better choice for
- *   most users because assuming a too high display refresh rate
- *   avoids micro stuttering caused by missed frames if the vsync
- *   is enabled. The price are small and hard to notice timing
- *   problems.
- *
- * * SDL returns only full integers. In most cases they're rounded
- *   up, but in some cases - likely depending on the GPU driver -
- *   they're rounded down. If the value is rounded up, we'll see
- *   some small and nard to notice timing problems. If the value
- *   is rounded down frames will be missed. Both is only relevant
- *   if the vsync is enabled.
+ * Returns the current display refresh rate.
  */
-int
+float
 GLimp_GetRefreshRate(void)
 {
 
 	if (vid_displayrefreshrate->value > -1 ||
 			vid_displayrefreshrate->modified)
 	{
-		glimp_refreshRate = ceil(vid_displayrefreshrate->value);
+		glimp_refreshRate = vid_displayrefreshrate->value;
 		vid_displayrefreshrate->modified = false;
 	}
-
-	if (glimp_refreshRate == -1)
+	else if (glimp_refreshRate == -1)
 	{
 		SDL_DisplayMode mode;
 

src/client/vid/glimp_sdl3.c

@@ -41,7 +41,7 @@
 
 #include <SDL3/SDL.h>
 
-int glimp_refreshRate = -1;
+float glimp_refreshRate = -1.0f;
 
 static cvar_t *vid_displayrefreshrate;
 static cvar_t *vid_displayindex;
@@ -795,37 +795,19 @@ GLimp_GrabInput(qboolean grab)
 }
 
 /*
- * Returns the current display refresh rate. There're 2 limitations:
- *
- * * The timing code in frame.c only understands full integers, so
- *   values given by vid_displayrefreshrate are always round up. For
- *   example 59.95 become 60. Rounding up is the better choice for
- *   most users because assuming a too high display refresh rate
- *   avoids micro stuttering caused by missed frames if the vsync
- *   is enabled. The price are small and hard to notice timing
- *   problems.
- *
- * * SDL returns only full integers. In most cases they're rounded
- *   up, but in some cases - likely depending on the GPU driver -
- *   they're rounded down. If the value is rounded up, we'll see
- *   some small and nard to notice timing problems. If the value
- *   is rounded down frames will be missed. Both is only relevant
- *   if the vsync is enabled.
- *
- * TODO SDL 3: Refactor this to floats?
+ * Returns the current display refresh rate.
  */
-int
+float
 GLimp_GetRefreshRate(void)
 {
 
 	if (vid_displayrefreshrate->value > -1 ||
 			vid_displayrefreshrate->modified)
 	{
-		glimp_refreshRate = ceil(vid_displayrefreshrate->value);
+		glimp_refreshRate = vid_displayrefreshrate->value;
 		vid_displayrefreshrate->modified = false;
 	}
-
-	if (glimp_refreshRate == -1)
+	else if (glimp_refreshRate == -1)
 	{
 		const SDL_DisplayMode *mode;
 		int curdisplay;

src/client/vid/header/vid.h

@@ -54,7 +54,7 @@ void	VID_MenuDraw(void);
 const char *VID_MenuKey(int);
 
 // Stuff provided by platform backend.
-extern int glimp_refreshRate;
+extern float glimp_refreshRate;
 
 const char **GLimp_GetDisplayIndices(void);
 int GLimp_GetWindowDisplayIndex(void);
@@ -64,7 +64,7 @@ void GLimp_Shutdown(void);
 qboolean GLimp_InitGraphics(int fullscreen, int *pwidth, int *pheight);
 void GLimp_ShutdownGraphics(void);
 void GLimp_GrabInput(qboolean grab);
-int GLimp_GetRefreshRate(void);
+float GLimp_GetRefreshRate(void);
 qboolean GLimp_GetDesktopMode(int *pwidth, int *pheight);
 
 #endif

src/common/frame.c

@@ -53,7 +53,7 @@ cvar_t *showtrace;
 
 // Forward declarations
 #ifndef DEDICATED_ONLY
-int GLimp_GetRefreshRate(void);
+float GLimp_GetRefreshRate(void);
 qboolean R_IsVSyncActive(void);
 #endif
 
@@ -556,7 +556,7 @@ Qcommon_Frame(int usec)
 	// Calculate target and renderframerate.
 	if (R_IsVSyncActive())
 	{
-		int refreshrate = GLimp_GetRefreshRate();
+		float refreshrate = GLimp_GetRefreshRate();
 
 		// using refreshRate - 2, because targeting a value slightly below the
 		// (possibly not 100% correctly reported) refreshRate would introduce jittering, so only