handle fullscreen mode change properly

This better replicates the old behavior of SDL2's fullscreen style. SDL3 defaults to a fullscreen-window
style unless you specifically set a fullscreen display mode.

Note that gr_activate() must default to true in order to avoid a weird sequence of window mode
changes on startup when using fullscreen.

Author: notimaginative

code/globalincs/windebug.cpp

@@ -40,7 +40,7 @@
 #	include "globalincs/mspdb_callstack.h"
 #endif
 
-extern void gr_activate(int active);
+extern void gr_activate(bool active);
 
 #ifndef _ASSERT
   #ifndef _DEBUG

code/graphics/2d.cpp

@@ -2116,10 +2116,9 @@ bool gr_init(std::unique_ptr<os::GraphicsOperations>&& graphicsOps, int d_mode,
 	return true;
 }
 
-int gr_activated = 0;
-void gr_activate(int active)
+static bool gr_activated = true;	// start activated
+void gr_activate(bool active)
 {
-
 	if (gr_activated == active) {
 		return;
 	}
@@ -3317,4 +3316,4 @@ bool gr_lua_context_active() {
 	}
 
 	return gr_lua_screen.active;
-}
+}

code/graphics/2d.h

@@ -1063,7 +1063,7 @@ extern int gr_get_dynamic_font_lines(int number_default_lines);
 extern io::mouse::Cursor* Web_cursor;
 
 // Called by OS when application gets/looses focus
-extern void gr_activate(int active);
+extern void gr_activate(bool active);
 
 #define GR_CALL(x) (x)
 

code/osapi/dialogs.cpp

@@ -233,7 +233,7 @@ namespace os
 			boxData.title = "Error!";
 			boxData.window = getDialogParent();
 
-			gr_activate(0);
+			gr_activate(false);
 
 			int buttonId;
 			if ( !SDL_ShowMessageBox(&boxData, &buttonId) )
@@ -255,7 +255,7 @@ namespace os
 				break;
 			}
 
-			gr_activate(1);
+			gr_activate(true);
 		}
 
 		void Error(const char * filename, int line, const char * format, ...)
@@ -317,7 +317,7 @@ namespace os
 			boxData.title = "Error!";
 			boxData.window = getDialogParent();
 
-			gr_activate(0);
+			gr_activate(false);
 
 			int buttonId;
 			if ( !SDL_ShowMessageBox(&boxData, &buttonId) )
@@ -335,7 +335,7 @@ namespace os
 				Int3();
 				break;
 			}
-			gr_activate(1);
+			gr_activate(true);
 		}
 
 		// Actual implementation of the warning function. Used by the various warning functions
@@ -385,7 +385,7 @@ namespace os
 			boxData.title = "Warning!";
 			boxData.window = getDialogParent();
 
-			gr_activate(0);
+			gr_activate(false);
 
 			int buttonId;
 			if ( !SDL_ShowMessageBox(&boxData, &buttonId) )
@@ -407,7 +407,7 @@ namespace os
 				break;
 			}
 
-			gr_activate(1);
+			gr_activate(true);
 		}
 
 
@@ -487,11 +487,11 @@ namespace os
 			SCP_string boxMessage = truncateLines(boxMsgStream, Messagebox_lines);
 			boxMessage += "\n[ This info is in the clipboard so you can paste it somewhere now ]\n";
 
-			gr_activate(0);
+			gr_activate(false);
 
 			SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_INFORMATION, "Information", boxMessage.c_str(), getDialogParent());
 
-			gr_activate(1);
+			gr_activate(true);
 		}
 
 		void Message(MessageType type, const char* message, const char* title)

code/osapi/osapi.cpp

@@ -638,15 +638,15 @@ void debug_int3(const char *file, int line)
 {
 	mprintf(("Int3(): From %s at line %d\n", file, line));
 
-	gr_activate(0);
+	gr_activate(false);
 
 	mprintf(("%s\n", dump_stacktrace().c_str()));
 
 #ifndef NDEBUG
 	SDL_TriggerBreakpoint();
 #endif
 
-	gr_activate(1);
+	gr_activate(true);
 }
 
 namespace os

freespace2/SDLGraphicsOperations.cpp

@@ -148,9 +148,26 @@ class SDLWindowViewPort: public os::Viewport {
 				SDL_SetWindowFullscreen(_window, false);
 				SDL_SetWindowBordered(_window, false);
 				break;
-			case os::ViewportState::Fullscreen:
+			case os::ViewportState::Fullscreen: {
+				SDL_DisplayMode target;
+				int width, height;
+
+				if (SDL_GetWindowSizeInPixels(_window, &width, &height)) {
+					if (SDL_GetClosestFullscreenDisplayMode(SDL_GetDisplayForWindow(_window),
+															width, height, 0.0f, true, &target))
+					{
+						SDL_SetWindowFullscreenMode(_window, &target);
+					}
+				}
+
+				// NOTE: This can be buggy if the mode failed to set since FSO
+				// doesn't account for a difference between assumed window size
+				// and actual window size. This can present as screen anomalies
+				// such as distortion, mirroring, or flickering.
 				SDL_SetWindowFullscreen(_window, true);
+
 				break;
+			}
 			default:
 				UNREACHABLE("Invalid window state!");
 				break;
@@ -229,7 +246,10 @@ std::unique_ptr<os::Viewport> SDLGraphicsOperations::createViewport(const os::Vi
 		windowflags |= SDL_WINDOW_BORDERLESS;
 	}
 	if (props.flags[os::ViewPortFlags::Fullscreen]) {
-		windowflags |= SDL_WINDOW_FULLSCREEN;
+		// don't set window flag here since we need to alter the display mode
+		// first and that can only be done after the window is created
+		//
+		// windowflags |= SDL_WINDOW_FULLSCREEN;
 	}
 	if (props.flags[os::ViewPortFlags::Resizeable]) {
 		windowflags |= SDL_WINDOW_RESIZABLE;
@@ -273,6 +293,21 @@ std::unique_ptr<os::Viewport> SDLGraphicsOperations::createViewport(const os::Vi
 		return nullptr;
 	}
 
+	// switch to fullscreen if we should
+	if (props.flags[os::ViewPortFlags::Fullscreen]) {
+		SDL_DisplayMode target;
+
+		if (SDL_GetClosestFullscreenDisplayMode(props.display, width, height, 0.0f, true, &target)) {
+			SDL_SetWindowFullscreenMode(window, &target);
+		}
+
+		// NOTE: This can be buggy if the mode failed to set since FSO doesn't
+		// account for a difference between assumed window size and actual window
+		// size. This can present as screen anomalies such as distortion, mirroring,
+		// or flickering.
+		SDL_SetWindowFullscreen(window, true);
+	}
+
 	SDL_SetWindowPosition(window, x, y);
 	SDL_RaiseWindow(window);