[rcore_desktop_sdl] fix: handle monitor ID correctly on SDL3 (#5290)

SDL3 uses ID when dealing with monitors, unlike SDL2 which uses Index
for the same thing. This problem was already fixed in multiple places
by use of preprocessor branches, so I did the very same thing.

Please, notice that this is a pretty bad solution to this problem,
and I only did it to keep it consistent with the rest of the code.
The more about why it's not correct is mentioned here:
https://github.com/raysan5/raylib/issues/5256#issuecomment-3429156919
Hopefully, someone will refactor it someday :)

Fixes: https://github.com/raysan5/raylib/issues/5256

src/platforms/rcore_desktop_sdl.c

@@ -837,7 +837,11 @@ void SetWindowPosition(int x, int y)
 void SetWindowMonitor(int monitor)
 {
     const int monitorCount = SDL_GetNumVideoDisplays();
+#if defined(USING_VERSION_SDL3) // SDL3 Migration: Monitor is an id instead of index now, returns 0 on failure
+    if ((monitor > 0) && (monitor <= monitorCount))
+#else
     if ((monitor >= 0) && (monitor < monitorCount))
+#endif
     {
         // NOTE:
         // 1. SDL started supporting moving exclusive fullscreen windows between displays on SDL3,
@@ -961,7 +965,11 @@ int GetCurrentMonitor(void)
 Vector2 GetMonitorPosition(int monitor)
 {
     const int monitorCount = SDL_GetNumVideoDisplays();
+#if defined(USING_VERSION_SDL3) // SDL3 Migration: Monitor is an id instead of index now, returns 0 on failure
+    if ((monitor > 0) && (monitor <= monitorCount))
+#else
     if ((monitor >= 0) && (monitor < monitorCount))
+#endif
     {
         SDL_Rect displayBounds;
 
@@ -985,7 +993,11 @@ int GetMonitorWidth(int monitor)
     int width = 0;
 
     const int monitorCount = SDL_GetNumVideoDisplays();
+#if defined(USING_VERSION_SDL3) // SDL3 Migration: Monitor is an id instead of index now, returns 0 on failure
+    if ((monitor > 0) && (monitor <= monitorCount))
+#else
     if ((monitor >= 0) && (monitor < monitorCount))
+#endif
     {
         SDL_DisplayMode mode;
         SDL_GetCurrentDisplayMode(monitor, &mode);
@@ -1002,7 +1014,11 @@ int GetMonitorHeight(int monitor)
     int height = 0;
 
     const int monitorCount = SDL_GetNumVideoDisplays();
+#if defined(USING_VERSION_SDL3) // SDL3 Migration: Monitor is an id instead of index now, returns 0 on failure
+    if ((monitor > 0) && (monitor <= monitorCount))
+#else
     if ((monitor >= 0) && (monitor < monitorCount))
+#endif
     {
         SDL_DisplayMode mode;
         SDL_GetCurrentDisplayMode(monitor, &mode);
@@ -1019,7 +1035,11 @@ int GetMonitorPhysicalWidth(int monitor)
     int width = 0;
 
     const int monitorCount = SDL_GetNumVideoDisplays();
+#if defined(USING_VERSION_SDL3) // SDL3 Migration: Monitor is an id instead of index now, returns 0 on failure
+    if ((monitor > 0) && (monitor <= monitorCount))
+#else
     if ((monitor >= 0) && (monitor < monitorCount))
+#endif
     {
         float ddpi = 0.0f;
         SDL_GetDisplayDPI(monitor, &ddpi, NULL, NULL);
@@ -1039,7 +1059,11 @@ int GetMonitorPhysicalHeight(int monitor)
     int height = 0;
 
     const int monitorCount = SDL_GetNumVideoDisplays();
+#if defined(USING_VERSION_SDL3) // SDL3 Migration: Monitor is an id instead of index now, returns 0 on failure
+    if ((monitor > 0) && (monitor <= monitorCount))
+#else
     if ((monitor >= 0) && (monitor < monitorCount))
+#endif
     {
         float ddpi = 0.0f;
         SDL_GetDisplayDPI(monitor, &ddpi, NULL, NULL);
@@ -1059,7 +1083,11 @@ int GetMonitorRefreshRate(int monitor)
     int refresh = 0;
 
     const int monitorCount = SDL_GetNumVideoDisplays();
+#if defined(USING_VERSION_SDL3) // SDL3 Migration: Monitor is an id instead of index now, returns 0 on failure
+    if ((monitor > 0) && (monitor <= monitorCount))
+#else
     if ((monitor >= 0) && (monitor < monitorCount))
+#endif
     {
         SDL_DisplayMode mode;
         SDL_GetCurrentDisplayMode(monitor, &mode);
@@ -1075,7 +1103,14 @@ const char *GetMonitorName(int monitor)
 {
     const int monitorCount = SDL_GetNumVideoDisplays();
 
-    if ((monitor >= 0) && (monitor < monitorCount)) return SDL_GetDisplayName(monitor);
+#if defined(USING_VERSION_SDL3) // SDL3 Migration: Monitor is an id instead of index now, returns 0 on failure
+    if ((monitor > 0) && (monitor <= monitorCount))
+#else
+    if ((monitor >= 0) && (monitor < monitorCount))
+#endif
+    {
+        return SDL_GetDisplayName(monitor);
+    }
     else TRACELOG(LOG_WARNING, "SDL: Failed to find selected monitor");
 
     return "";