From 6b11f43302db47624baa08960fb4548ef3091ac4 Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Thu, 19 Sep 2024 22:43:34 -0500
Subject: [PATCH] Don't set the output rect until after modesetting

It's possible that modesetting will also change the resolution
not just the refresh rate. This can happen in cases where the
CRTC is currently set to 4K 30 Hz and we choose 1080p 60 Hz as
a better mode match for displaying a 1080p 60 FPS stream.
---
 app/streaming/video/ffmpeg-renderers/drm.cpp | 32 +++++++++++++++++---
 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/app/streaming/video/ffmpeg-renderers/drm.cpp b/app/streaming/video/ffmpeg-renderers/drm.cpp
index b539c192..885baf4d 100644
--- a/app/streaming/video/ffmpeg-renderers/drm.cpp
+++ b/app/streaming/video/ffmpeg-renderers/drm.cpp
@@ -166,6 +166,7 @@ DrmRenderer::DrmRenderer(AVHWDeviceType hwDeviceType, IFFmpegRenderer *backendRe
       m_ColorspaceProp(nullptr),
       m_Version(nullptr),
       m_HdrOutputMetadataBlobId(0),
+      m_OutputRect{},
       m_SwFrameMapper(this),
       m_CurrentSwFrameIdx(0)
 #ifdef HAVE_EGL
@@ -297,6 +298,30 @@ void DrmRenderer::prepareToRender()
                      "SDL_CreateRenderer() failed: %s",
                      SDL_GetError());
     }
+
+    // Set the output rect to match the new CRTC size after modesetting
+    m_OutputRect.x = m_OutputRect.y = 0;
+    drmModeCrtc* crtc = drmModeGetCrtc(m_DrmFd, m_CrtcId);
+    if (crtc != nullptr) {
+        SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
+                    "CRTC size after modesetting: %ux%u",
+                    crtc->width,
+                    crtc->height);
+        m_OutputRect.w = crtc->width;
+        m_OutputRect.h = crtc->height;
+        drmModeFreeCrtc(crtc);
+    }
+    else {
+        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                     "drmModeGetCrtc() failed: %d",
+                     errno);
+
+        SDL_GetWindowSize(m_Window, &m_OutputRect.w, &m_OutputRect.h);
+        SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION,
+                    "Guessing CRTC is window size: %dx%d",
+                    m_OutputRect.w,
+                    m_OutputRect.h);
+    }
 }
 
 bool DrmRenderer::getPropertyByName(drmModeObjectPropertiesPtr props, const char* name, uint64_t *value) {
@@ -523,12 +548,7 @@ bool DrmRenderer::initialize(PDECODER_PARAMETERS params)
     int crtcIndex = -1;
     for (int i = 0; i < resources->count_crtcs; i++) {
         if (resources->crtcs[i] == m_CrtcId) {
-            drmModeCrtc* crtc = drmModeGetCrtc(m_DrmFd, resources->crtcs[i]);
             crtcIndex = i;
-            m_OutputRect.x = m_OutputRect.y = 0;
-            m_OutputRect.w = crtc->width;
-            m_OutputRect.h = crtc->height;
-            drmModeFreeCrtc(crtc);
             break;
         }
     }
@@ -1240,6 +1260,8 @@ void DrmRenderer::renderFrame(AVFrame* frame)
     int err;
     SDL_Rect src, dst;
 
+    SDL_assert(m_OutputRect.w > 0 && m_OutputRect.h > 0);
+
     src.x = src.y = 0;
     src.w = frame->width;
     src.h = frame->height;