Workaround for Wayland with HiDPI settings

Wayland with hidpi settings did some double scaling which resulted in
too large windows.

When we detect a wayland session (via external C code) we 'fix' the
wrong screen geometry.

Author: AndreasBilke

src/CMakeLists.txt

@@ -57,6 +57,7 @@ endif()
 
 CONFIGURE_FILE(${CMAKE_CURRENT_SOURCE_DIR}/paths.in ${CMAKE_CURRENT_BINARY_DIR}/paths.vala)
 
+file (GLOB_RECURSE C_SRC RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} *.c)
 file (GLOB_RECURSE VALA_SRC RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} *.vala)
 list(REMOVE_ITEM VALA_SRC paths.vala)
 if (MOVIES)
@@ -87,11 +88,12 @@ GENERATE_VAPI
     presenter
 CUSTOM_VAPIS
     ${CMAKE_CURRENT_BINARY_DIR}/paths.vala
+    ${CMAKE_CURRENT_SOURCE_DIR}/custom_binding.vapi
 )
 
-
 add_executable(pdfpc
     ${VALA_C}
+    ${C_SRC}
 )
 
 # explicitly add libraries (needed e.g. for Fedora 13+)

src/classes/window/fullscreen.vala

@@ -108,6 +108,12 @@ namespace pdfpc.Window {
             }
 
             this.gdk_scale = this.screen_to_use.get_monitor_scale_factor(this.screen_num_to_use);
+            if (Pdfpc.is_Wayland_backend()) {
+                // See issue 214. Wayland is doing some double scaling therefore
+                // we are lying about the actual screen size
+                this.screen_geometry.width /= this.gdk_scale;
+                this.screen_geometry.height /= this.gdk_scale;
+            }
 
             this.overlay_layout = new Gtk.Overlay();
             this.pointer_drawing_surface = new Gtk.DrawingArea();

src/custom_binding.vapi

@@ -0,0 +1,8 @@
+[CCode (cheader_filename = "display_backend.h")]
+namespace Pdfpc {
+    [CCode (cname = "is_Wayland_backend")]
+    bool is_Wayland_backend();
+
+    [CCode (cname = "is_X11_backend")]
+    bool is_X11_backend();
+}

src/display_backend.c

@@ -0,0 +1,34 @@
+#include "display_backend.h"
+
+#include <stdio.h>
+
+#include <gdk/gdk.h>
+#ifdef GDK_WINDOWING_X11
+#include <gdk/gdkx.h>
+#endif
+#ifdef GDK_WINDOWING_WAYLAND
+#include <gdk/gdkwayland.h>
+#endif
+
+bool is_Wayland_backend() {
+    GdkDisplay *gdk_display = gdk_display_get_default();
+    #ifdef GDK_WINDOWING_WAYLAND
+    if (GDK_IS_WAYLAND_DISPLAY(gdk_display)) {
+        return true;
+    }
+    #endif
+
+    return false;
+}
+
+bool is_X11_backend() {
+    GdkDisplay *gdk_display = gdk_display_get_default();
+    #ifdef GDK_WINDOWING_X11
+    if (GDK_IS_X11_DISPLAY(gdk_display)) {
+        return true;
+    }
+    #endif
+
+    return false;
+}
+

src/display_backend.h

@@ -0,0 +1,9 @@
+#ifndef DISPLAY_BACKEND_H
+#define DISPLAY_BACKEND_H
+
+#include <stdbool.h>
+
+bool is_Wayland_backend();
+bool is_X11_backend();
+
+#endif