headless test

.dockerignore

@@ -0,0 +1,3 @@
+build
+Dockerfile
+output.png

.github/workflows/build.yml

@@ -0,0 +1,19 @@
+name: Build inside Docker
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Build Docker image
+      run: docker build .

.gitignore

@@ -1,2 +1,3 @@
 build
 .vscode
+*.png

CMakeLists.txt

@@ -19,3 +19,5 @@ target_link_libraries(${PROJECT_NAME} PRIVATE
   Qt6::Quick
   Qt6::Widgets
 )
+
+install(TARGETS ${PROJECT_NAME} DESTINATION bin)

Dockerfile

@@ -0,0 +1,21 @@
+FROM ubuntu:latest
+
+RUN apt update && \
+    apt install -y \
+        xvfb mesa-utils \
+        cmake \
+        build-essential \
+        qt6-declarative-dev \
+        qml6-module-qtquick \
+        qml6-module-qtquick-controls \
+        qml6-module-qtqml-workerscript \
+        qml6-module-qtquick-templates
+
+WORKDIR /app
+COPY . .
+RUN cmake -B build -S .
+RUN cmake --build build --parallel --target install
+
+COPY entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh
+CMD ["/entrypoint.sh"]

README.md

@@ -1,13 +1,36 @@
+# ![status](https://github.com/krjakbrjak/offscreen_rendering/actions/workflows/build.yml/badge.svg)
+
 # Offscreen Rendering
 
-Rendering into a custom framebuffer, also known as off-screen rendering or rendering to a texture, plays a crucial role in numerous scenarios within computer graphics and game development. This repo is just an example that demonstrates how this can be effortlessly achieved using the Qt framework (version 6.6 is used).
+Rendering into a custom framebuffer, also known as off-screen rendering or rendering to a texture, plays a crucial role in numerous scenarios within computer graphics and game development. This repo is just an example that demonstrates how this can be achieved using the Qt framework (version 6).
 
-![main.qml](screenshot.png)
+![Screenshot of Qt offscreen rendering example](screenshot.png)
 
 ## Build and run
 
 ```bash
 cmake -B build -S .
 cmake --build build --parallel
-./build/offscreen_sample
-```
+```
+
+## Dependencies
+
+This project uses Qt (Qt Quick, Qt QML, Qt OpenGL). The required Ubuntu packages for Qt and other dependencies are listed in the Dockerfile included in this repository.
+
+## Usage
+
+When running inside Docker, the output image will be written to a mounted folder. Specify the output path using the `--output` or `-o` CLI argument:
+
+```sh
+./build/offscreen_sample --output /output/image.png
+```
+
+Make sure to mount a host directory to `/output` in your Docker container to access the generated image.
+
+## Example Docker run (headless mode)
+
+```sh
+docker run --rm -u $(id -u):$(id -g) -v $(pwd)/output:/output $(docker build . -q)
+```
+
+This will save the rendered image to the `output` folder on your host machine.

entrypoint.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+pkill Xvfb || true
+
+Xvfb :99 -screen 0 1024x768x24 2>/dev/null &
+XVFB_PID=$!
+export DISPLAY=:99
+export QT_OPENGL=desktop
+
+# Trap all common signals to ensure Xvfb is killed
+trap "kill $XVFB_PID" EXIT SIGHUP SIGINT SIGTERM SIGQUIT
+
+QT_QPA_PLATFORM=xcb offscreen_sample -o /output/image.png

main.cpp

@@ -1,5 +1,6 @@
 #include <QApplication>
-#include <QLabel>
+#include <QCommandLineOption>
+#include <QCommandLineParser>
 #include <QOffscreenSurface>
 #include <QOpenGLContext>
 #include <QOpenGLFramebufferObject>
@@ -14,11 +15,29 @@
 #include <QSurfaceFormat>
 
 int main(int argc, char **argv) {
-  QApplication app{argc, argv};
-
+  QGuiApplication app(argc, argv);
+
+  QCommandLineParser parser;
+  parser.setApplicationDescription("Offscreen Qt Quick Renderer");
+  parser.addHelpOption();
+  QCommandLineOption outputOption({"o", "output"}, "Path to output image",
+                                  "output");
+  parser.addOption(outputOption);
+  parser.process(app);
+
+  QString outputPath = parser.value(outputOption);
+  if (outputPath.isEmpty()) {
+    qCritical() << "No output path specified. Use --output <path> or -o <path>";
+    return 1;
+  }
   QSurfaceFormat format;
   format.setMajorVersion(4);
   format.setMinorVersion(6);
+  if (QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL) {
+    format.setRenderableType(QSurfaceFormat::OpenGL);
+  } else {
+    format.setRenderableType(QSurfaceFormat::OpenGLES);
+  }
 
   QOpenGLContext gl_ctx;
   gl_ctx.setFormat(format);
@@ -61,12 +80,6 @@ int main(int argc, char **argv) {
   auto tg = QQuickRenderTarget::fromOpenGLTexture(fb.texture(), fb.size());
   window.setRenderTarget(tg);
 
-  // Label that displays the content of the custom framebuffer.
-  QLabel label;
-  label.setFixedWidth(fb.size().width());
-  label.setFixedHeight(fb.size().height());
-  label.show();
-
   QObject::connect(
       &control, &QQuickRenderControl::sceneChanged, &control,
       [&] {
@@ -76,8 +89,8 @@ int main(int argc, char **argv) {
         control.render();
         control.endFrame();
 
-        // To simplify, just display the image.
-        label.setPixmap(QPixmap::fromImage(fb.toImage()));
+        // To simplify, just save the image.
+        fb.toImage().save(outputPath);
       },
       Qt::QueuedConnection);