Feature: Variable GUI scale.

GUI scale is now variable from 100% to 500%, and no longer restricted to
powers-of-2.

src/video/cocoa/cocoa_wnd.mm

@@ -1269,7 +1269,7 @@ void CocoaDialog(const char *title, const char *message, const char *buttonLabel
 /** Screen the window is on changed. */
 - (void)windowDidChangeBackingProperties:(NSNotification *)notification
 {
-	bool did_adjust = AdjustGUIZoom();
+	bool did_adjust = AdjustGUIZoom(true);
 
 	/* Reallocate screen buffer if necessary. */
 	driver->AllocateBackingStore();

src/video/video_driver.hpp

@@ -167,15 +167,13 @@ public:
 	}
 
 	/**
-	 * Get a suggested default GUI zoom taking screen DPI into account.
+	 * Get a suggested default GUI scale taking screen DPI into account.
 	 */
-	virtual ZoomLevel GetSuggestedUIZoom()
+	virtual int GetSuggestedUIScale()
 	{
 		float dpi_scale = this->GetDPIScale();
 
-		if (dpi_scale >= 3.0f) return ZOOM_LVL_NORMAL;
-		if (dpi_scale >= 1.5f) return ZOOM_LVL_OUT_2X;
-		return ZOOM_LVL_OUT_4X;
+		return Clamp(dpi_scale * 100, MIN_INTERFACE_SCALE, MAX_INTERFACE_SCALE);
 	}
 
 	virtual const char *GetInfoString() const

src/video/win32_v.cpp

@@ -675,7 +675,7 @@ LRESULT CALLBACK WndProcGdi(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
 		}
 
 		case WM_DPICHANGED: {
-			auto did_adjust = AdjustGUIZoom();
+			auto did_adjust = AdjustGUIZoom(true);
 
 			/* Resize the window to match the new DPI setting. */
 			RECT *prcNewWindow = (RECT *)lParam;