Drop gScreenToDisplay switch and use function table

Saves some bytes

ui/ui.c

@@ -14,6 +14,7 @@
  *     limitations under the License.
  */
 
+#include <assert.h>
 #include <string.h>
 
 #include "app/chFrScanner.h"
@@ -34,6 +35,7 @@
 #include "ui/menu.h"
 #include "ui/scanner.h"
 #include "ui/ui.h"
+#include "../misc.h"
 
 GUI_DisplayType_t gScreenToDisplay;
 GUI_DisplayType_t gRequestDisplayScreen = DISPLAY_INVALID;
@@ -42,36 +44,27 @@ uint8_t           gAskForConfirmation;
 bool              gAskToSave;
 bool              gAskToDelete;
 
+
+void (*UI_DisplayFunctions[])(void) = {
+	[DISPLAY_MAIN] = &UI_DisplayMain,
+	[DISPLAY_MENU] = &UI_DisplayMenu,
+	[DISPLAY_SCANNER] = &UI_DisplayScanner,
+
+#ifdef ENABLE_FMRADIO
+	[DISPLAY_FM] = &UI_DisplayFM,
+#endif
+
+#ifdef ENABLE_AIRCOPY
+	[DISPLAY_AIRCOPY] = &UI_DisplayAircopy,
+#endif
+};
+
+static_assert(ARRAY_SIZE(UI_DisplayFunctions) == DISPLAY_N_ELEM);
+
 void GUI_DisplayScreen(void)
 {
-	switch (gScreenToDisplay)
-	{
-		case DISPLAY_MAIN:
-			UI_DisplayMain();
-			break;
-
-		#ifdef ENABLE_FMRADIO
-			case DISPLAY_FM:
-				UI_DisplayFM();
-				break;
-		#endif
-		
-		case DISPLAY_MENU:
-			UI_DisplayMenu();
-			break;
-
-		case DISPLAY_SCANNER:
-			UI_DisplayScanner();
-			break;
-
-		#ifdef ENABLE_AIRCOPY
-			case DISPLAY_AIRCOPY:
-				UI_DisplayAircopy();
-				break;
-		#endif
-
-		default:
-			break;
+	if (gScreenToDisplay != DISPLAY_INVALID) {
+		UI_DisplayFunctions[gScreenToDisplay]();
 	}
 }
 

ui/ui.h

@@ -23,10 +23,18 @@
 enum GUI_DisplayType_t
 {
 	DISPLAY_MAIN = 0,
-	DISPLAY_FM,
 	DISPLAY_MENU,
 	DISPLAY_SCANNER,
+
+#ifdef ENABLE_FMRADIO
+	DISPLAY_FM,
+#endif
+
+#ifdef ENABLE_AIRCOPY
 	DISPLAY_AIRCOPY,
+#endif
+
+	DISPLAY_N_ELEM,
 	DISPLAY_INVALID = 0xFFu
 };