Detect native panel resolution on Retina displays. Fixes #59

app/streaming/session.cpp

@@ -1,5 +1,6 @@
 #include "session.hpp"
 #include "settings/streamingpreferences.h"
+#include "streaming/streamutils.h"
 
 #include <Limelight.h>
 #include <SDL.h>
@@ -544,7 +545,7 @@ void Session::getWindowDimensions(bool fullScreen,
     else if (fullScreen) {
         for (int i = 0; i < SDL_GetNumVideoDisplays(); i++) {
             SDL_DisplayMode mode;
-            if (SDL_GetDesktopDisplayMode(i, &mode) == 0 &&
+            if (StreamUtils::getRealDesktopMode(i, &mode) &&
                     m_ActiveVideoWidth == mode.w &&
                     m_ActiveVideoHeight == mode.h) {
                 SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
@@ -603,7 +604,7 @@ void Session::updateOptimalWindowDisplayMode()
     int displayIndex = SDL_GetWindowDisplayIndex(m_Window);
 
     // Get the native desktop resolution
-    if (SDL_GetDesktopDisplayMode(displayIndex, &desktopMode) == 0) {
+    if (StreamUtils::getRealDesktopMode(displayIndex, &desktopMode)) {
         // Start with the native desktop resolution and try to find
         // the highest refresh rate that our stream FPS evenly divides.
         bestMode = desktopMode;
@@ -757,7 +758,7 @@ void Session::exec()
                                 y,
                                 width,
                                 height,
-                                0);
+                                SDL_WINDOW_ALLOW_HIGHDPI);
     if (!m_Window) {
         SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
                      "SDL_CreateWindow() failed: %s",

app/streaming/streamutils.cpp

@@ -1,5 +1,11 @@
 #include "streamutils.h"
 
+#include <Qt>
+
+#ifdef Q_OS_DARWIN
+#include <ApplicationServices/ApplicationServices.h>
+#endif
+
 void StreamUtils::scaleSourceToDestinationSurface(SDL_Rect* src, SDL_Rect* dst)
 {
     int dstH = dst->w * src->h / src->w;
@@ -18,3 +24,58 @@ void StreamUtils::scaleSourceToDestinationSurface(SDL_Rect* src, SDL_Rect* dst)
         SDL_assert(dst->h * src->w / src->h <= dst->w);
     }
 }
+
+bool StreamUtils::getRealDesktopMode(int displayIndex, SDL_DisplayMode* mode)
+{
+#ifdef Q_OS_DARWIN
+#define MAX_DISPLAYS 16
+    CGDirectDisplayID displayIds[MAX_DISPLAYS];
+    uint32_t displayCount = 0;
+    CGGetActiveDisplayList(MAX_DISPLAYS, displayIds, &displayCount);
+    if (displayIndex >= displayCount) {
+        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                     "Too many displays: %d vs %d",
+                     displayIndex, displayCount);
+        return false;
+    }
+
+    SDL_zerop(mode);
+
+    // Retina displays have non-native resolutions both below and above (!) their
+    // native resolution, so it's impossible for us to figure out what's actually
+    // native on macOS using the SDL API alone. We'll talk to CoreGraphics to
+    // find the correct resolution and match it in our SDL list.
+    CFArrayRef modeList = CGDisplayCopyAllDisplayModes(displayIds[displayIndex], nullptr);
+    CFIndex count = CFArrayGetCount(modeList);
+    for (CFIndex i = 0; i < count; i++) {
+        auto cgMode = (CGDisplayModeRef)(CFArrayGetValueAtIndex(modeList, i));
+        if ((CGDisplayModeGetIOFlags(cgMode) & kDisplayModeNativeFlag) != 0) {
+            mode->w = static_cast<int>(CGDisplayModeGetWidth(cgMode));
+            mode->h = static_cast<int>(CGDisplayModeGetHeight(cgMode));
+            break;
+        }
+    }
+    CFRelease(modeList);
+
+    // Now find the SDL mode that matches the CG native mode
+    for (int i = 0; i < SDL_GetNumDisplayModes(displayIndex); i++) {
+        SDL_DisplayMode thisMode;
+        if (SDL_GetDisplayMode(displayIndex, i, &thisMode) == 0) {
+            if (thisMode.w == mode->w && thisMode.h == mode->h &&
+                    thisMode.refresh_rate >= mode->refresh_rate) {
+                *mode = thisMode;
+                break;
+            }
+        }
+    }
+#else
+    if (SDL_GetDesktopDisplayMode(displayIndex, mode) != 0) {
+        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                     "SDL_GetDesktopDisplayMode() failed: %s",
+                     SDL_GetError());
+        return false;
+    }
+#endif
+
+    return true;
+}

app/streaming/streamutils.h

@@ -7,4 +7,7 @@ class StreamUtils
 public:
     static
     void scaleSourceToDestinationSurface(SDL_Rect* src, SDL_Rect* dst);
+
+    static
+    bool getRealDesktopMode(int displayIndex, SDL_DisplayMode* mode);
 };

app/streaming/video/ffmpeg-renderers/pacer/pacer.cpp

@@ -1,4 +1,5 @@
 #include "pacer.h"
+#include "streaming/streamutils.h"
 
 #include "nullthreadedvsyncsource.h"
 
@@ -143,10 +144,7 @@ bool Pacer::initialize(SDL_Window* window, int maxVideoFps, bool enableVsync)
     }
     else {
         // Use the current display mode for windowed and borderless
-        if (SDL_GetCurrentDisplayMode(displayIndex, &mode) != 0) {
-            SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
-                         "SDL_GetCurrentDisplayMode() failed: %s",
-                         SDL_GetError());
+        if (!StreamUtils::getRealDesktopMode(displayIndex, &mode)) {
             return false;
         }
     }