Added support for scaling the output

* Added "Scale" user option, which can either by "Auto" or an explicit
  scaling factor. Its maximum value depends on the current resolution.

  The "Auto" factor is based on keeping the logical resolution on at
  least 800x600, wheres the maximum scale is based on keeping the
  logical resolution on at least 640x480.

* Enabled support for High DPI. This means the rendering target can now
  have a different resolution than the window size, which can happen on
  macOS, Windows and Wayland. The resulting scale is multiplied by the
  above user-controlled scale.

  Currently, this looks ugly for non-integer scales, which are not used
  on macOS and can only be configured on some Wayland compositors.

  Has not been tested on Windows.

* Simplified OpenGL initialization (moved out of _beginDraw).

* Made sure _beginDraw/_endDraw sets a clip area also for SDLGraphics.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/client.h b/src/client.h
index be591979..49780a38 100644
--- a/src/client.h
+++ b/src/client.h
@@ -213,7 +213,8 @@ public:
      * Should be called after the window has been resized. Makes sure the GUI
      * and game adapt to the new size.
      */
-    void videoResized(int width, int height);
+    void handleWindowSizeChanged(int width, int height);
+    void checkGraphicsSize();
 
     static bool isActive();
     static bool hasInputFocus();