Fix flashing menu transitions

Fixes #591

SourceX/DiabloUI/credits.cpp

@@ -275,7 +275,6 @@ BOOL UiCreditsDialog(int a1)
 			UiHandleEvents(&event);
 		}
 	} while (!endMenu && !credits_renderer.Finished());
-	BlackPalette();
 
 	return true;
 }

SourceX/DiabloUI/diabloui.cpp

@@ -564,15 +564,18 @@ int GetCenterOffset(int w, int bw)
 void LoadBackgroundArt(const char *pszFile)
 {
 	SDL_Color pPal[256];
-
-	fadeTc = 0;
-	fadeValue = 0;
 	LoadArt(pszFile, &ArtBackground, 1, pPal);
 	if (ArtBackground.surface == nullptr)
 		return;
 
 	LoadPalInMem(pPal);
 	ApplyGamma(logical_palette, orig_palette, 256);
+
+	fadeTc = 0;
+	fadeValue = 0;
+	BlackPalette();
+	SDL_FillRect(GetOutputSurface(), NULL, 0x000000);
+	RenderPresent();
 }
 
 void UiFadeIn()

SourceX/DiabloUI/mainmenu.cpp

@@ -72,7 +72,6 @@ BOOL UiMainMenuDialog(char *name, int *pdwResult, void (*fnSound)(char *file), i
 			}
 		}
 
-		BlackPalette();
 		mainmenu_Free();
 
 		if (gbSpawned && MainMenuResult == MAINMENU_REPLAY_INTRO) {

SourceX/DiabloUI/progress.cpp

@@ -128,7 +128,6 @@ BOOL UiProgressDialog(HWND window, char *msg, int enable, int (*fnfunc)(), int r
 			UiHandleEvents(&event);
 		}
 	}
-	BlackPalette();
 	progress_Free();
 
 	return progress == 100;

SourceX/DiabloUI/selconn.cpp

@@ -118,7 +118,6 @@ int UiSelectProvider(
 	while (!selconn_EndMenu) {
 		UiPollAndRender();
 	}
-	BlackPalette();
 	selconn_Free();
 
 	return selconn_ReturnValue;

SourceX/DiabloUI/selgame.cpp

@@ -176,7 +176,6 @@ bool IsDifficultyAllowed(int value)
 	}
 
 	selgame_Free();
-	BlackPalette();
 
 	if (value == 1)
 		UiSelOkDialog(title, "Your character must reach level 20 before you can enter a multiplayer game of Nightmare difficulty.", false);
@@ -235,7 +234,6 @@ void selgame_Password_Select(int value)
 			selgame_endMenu = true;
 		} else {
 			selgame_Free();
-			BlackPalette();
 			UiSelOkDialog("Multi Player Game", SDL_GetError(), false);
 			LoadBackgroundArt("ui_art\\selgame.pcx");
 			selgame_Password_Init(selgame_selectedGame);
@@ -251,7 +249,6 @@ void selgame_Password_Select(int value)
 		selgame_endMenu = true;
 	} else {
 		selgame_Free();
-		BlackPalette();
 		UiSelOkDialog("Multi Player Game", SDL_GetError(), false);
 		LoadBackgroundArt("ui_art\\selgame.pcx");
 		selgame_Password_Init(0);
@@ -275,7 +272,6 @@ int UiSelectGame(int a1, _SNETPROGRAMDATA *client_info, _SNETPLAYERDATA *user_in
 	while (!selgame_endMenu) {
 		UiPollAndRender();
 	}
-	BlackPalette();
 	selgame_Free();
 
 	return selgame_enteringGame;

SourceX/DiabloUI/selhero.cpp

@@ -240,7 +240,6 @@ void selhero_ClassSelector_Select(int value)
 {
 	if (gbSpawned && (value == 1 || value == 2)) {
 		selhero_Free();
-		BlackPalette();
 		UiSelOkDialog(nullptr, "The Rogue and Sorcerer are only available in the full retail version of Diablo. Visit https://www.gog.com/game/diablo to purchase.", false);
 		LoadBackgroundArt("ui_art\\selhero.pcx");
 		selhero_List_Select(selhero_SaveCount);
@@ -273,7 +272,6 @@ void selhero_Name_Select(int value)
 
 	if (!UiValidPlayerName(selhero_heroInfo.name)) {
 		selhero_Free();
-		BlackPalette();
 		UiSelOkDialog(title, "Invalid name. A name cannot contain spaces, reserved characters, or reserved words.\n", false);
 		LoadBackgroundArt("ui_art\\selhero.pcx");
 	} else {
@@ -281,7 +279,6 @@ void selhero_Name_Select(int value)
 		for (std::size_t i = 0; i < selhero_SaveCount; i++) {
 			if (strcasecmp(selhero_heros[i].name, selhero_heroInfo.name) == 0) {
 				selhero_Free();
-				BlackPalette();
 				char dialogText[256];
 				sprintf(dialogText, "Character already exists. Do you want to overwrite \"%s\"?", selhero_heroInfo.name);
 				overwrite = UiSelHeroYesNoDialog(title, dialogText);
@@ -370,7 +367,6 @@ BOOL UiSelHeroDialog(
 			UiRenderItems(SELHERO_DIALOG, size(SELHERO_DIALOG));
 			UiPollAndRender();
 		}
-		BlackPalette();
 		selhero_Free();
 
 		if (selhero_navigateYesNo) {

SourceX/DiabloUI/selok.cpp

@@ -79,8 +79,6 @@ void UiSelOkDialog(const char *title, const char *body, bool background)
 		UiPollAndRender();
 	}
 
-	BlackPalette();
-
 	selok_Free();
 }
 } // namespace dvl

SourceX/DiabloUI/selyesno.cpp

@@ -59,8 +59,6 @@ bool UiSelHeroYesNoDialog(const char *title, const char *body)
 		UiPollAndRender();
 	}
 
-	BlackPalette();
-
 	selyesno_Free();
 
 	return selyesno_value;

SourceX/DiabloUI/title.cpp

@@ -54,7 +54,6 @@ void UiTitleDialog()
 			UiHandleEvents(&event);
 		}
 	}
-	BlackPalette();
 
 	title_Free();
 }