From b0804ce048af2d6c9a7cd387325858cccd1b8658 Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Tue, 16 Aug 2022 00:25:49 -0500
Subject: [PATCH] Fix native resolution detection on high DPI wayland systems

---
 app/backend/systemproperties.cpp |  2 +-
 app/streaming/session.cpp        |  2 +-
 app/streaming/streamutils.cpp    | 27 +++++++++++++++++++++------
 app/streaming/streamutils.h      |  2 +-
 4 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/app/backend/systemproperties.cpp b/app/backend/systemproperties.cpp
index 6af5da5d..bd64c9d8 100644
--- a/app/backend/systemproperties.cpp
+++ b/app/backend/systemproperties.cpp
@@ -221,7 +221,7 @@ void SystemProperties::refreshDisplaysInternal()
                          SDL_GetError());
         }
 
-        if (StreamUtils::getRealDesktopMode(displayIndex, &desktopMode)) {
+        if (StreamUtils::getNativeDesktopMode(displayIndex, &desktopMode)) {
             if (desktopMode.w <= 8192 && desktopMode.h <= 8192) {
                 monitorNativeResolutions.insert(displayIndex, QRect(0, 0, desktopMode.w, desktopMode.h));
             }
diff --git a/app/streaming/session.cpp b/app/streaming/session.cpp
index cc057877..fc4d29cb 100644
--- a/app/streaming/session.cpp
+++ b/app/streaming/session.cpp
@@ -986,7 +986,7 @@ void Session::updateOptimalWindowDisplayMode()
         // If this doesn't fit the selected resolution, use the native
         // resolution of the panel (unscaled).
         if (desktopMode.w < m_ActiveVideoWidth || desktopMode.h < m_ActiveVideoHeight) {
-            if (!StreamUtils::getRealDesktopMode(displayIndex, &desktopMode)) {
+            if (!StreamUtils::getNativeDesktopMode(displayIndex, &desktopMode)) {
                 return;
             }
         }
diff --git a/app/streaming/streamutils.cpp b/app/streaming/streamutils.cpp
index c38eddbd..01889f66 100644
--- a/app/streaming/streamutils.cpp
+++ b/app/streaming/streamutils.cpp
@@ -94,7 +94,7 @@ int StreamUtils::getDisplayRefreshRate(SDL_Window* window)
     return mode.refresh_rate;
 }
 
-bool StreamUtils::getRealDesktopMode(int displayIndex, SDL_DisplayMode* mode)
+bool StreamUtils::getNativeDesktopMode(int displayIndex, SDL_DisplayMode* mode)
 {
 #ifdef Q_OS_DARWIN
 #define MAX_DISPLAYS 16
@@ -138,11 +138,26 @@ bool StreamUtils::getRealDesktopMode(int displayIndex, SDL_DisplayMode* mode)
         }
     }
 #else
-    if (SDL_GetDesktopDisplayMode(displayIndex, mode) != 0) {
-        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
-                     "SDL_GetDesktopDisplayMode() failed: %s",
-                     SDL_GetError());
-        return false;
+    // We need to get the true display resolution without DPI scaling (since we use High DPI).
+    // Windows returns the real display resolution here, even if DPI scaling is enabled.
+    // macOS and Wayland report a resolution that includes the DPI scaling factor. Picking
+    // the first mode on Wayland will get the native resolution without the scaling factor
+    // (and macOS is handled in the #ifdef above).
+    if (!strcmp(SDL_GetCurrentVideoDriver(), "wayland")) {
+        if (SDL_GetDisplayMode(displayIndex, 0, mode) != 0) {
+            SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                         "SDL_GetDisplayMode() failed: %s",
+                         SDL_GetError());
+            return false;
+        }
+    }
+    else {
+        if (SDL_GetDesktopDisplayMode(displayIndex, mode) != 0) {
+            SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                         "SDL_GetDesktopDisplayMode() failed: %s",
+                         SDL_GetError());
+            return false;
+        }
     }
 #endif
 
diff --git a/app/streaming/streamutils.h b/app/streaming/streamutils.h
index d4d72a6b..3567b829 100644
--- a/app/streaming/streamutils.h
+++ b/app/streaming/streamutils.h
@@ -29,7 +29,7 @@ public:
     void screenSpaceToNormalizedDeviceCoords(SDL_Rect* src, SDL_FRect* dst, int viewportWidth, int viewportHeight);
 
     static
-    bool getRealDesktopMode(int displayIndex, SDL_DisplayMode* mode);
+    bool getNativeDesktopMode(int displayIndex, SDL_DisplayMode* mode);
 
     static
     int getDisplayRefreshRate(SDL_Window* window);