feat: add GLDrawScope.terminate() method to stop the rendering thread from inside the render block

Author: silenium-dev

src/main/java/dev/silenium/compose/gl/fbo/FBOPool.kt

@@ -8,6 +8,7 @@ import dev.silenium.compose.gl.surface.GLDisplayScope
 import dev.silenium.compose.gl.surface.GLDisplayScopeImpl
 import dev.silenium.compose.gl.surface.GLDrawScope
 import dev.silenium.compose.gl.surface.GLDrawScopeImpl
+import kotlinx.coroutines.CancellationException
 import org.lwjgl.opengl.GL30.*
 import kotlin.contracts.ExperimentalContracts
 import kotlin.contracts.InvocationKind
@@ -92,7 +93,11 @@ class FBOPool(
                     glFlush()
                     fbo.unbind()
 
-                    Result.success(drawScope.redrawAfter)
+                    if (drawScope.terminate) {
+                        Result.failure(CancellationException("Rendering terminated"))
+                    } else {
+                        Result.success(drawScope.redrawAfter)
+                    }
                 }
             } ?: Result.failure(NoRenderFBOAvailable())
         }

src/main/java/dev/silenium/compose/gl/surface/GLDrawScope.kt

@@ -20,6 +20,11 @@ interface GLDrawScope {
      * @param duration The duration to redraw after. If null, a call to [GLSurfaceState.requestUpdate] is required to redraw.
      */
     fun redrawAfter(duration: Duration?)
+
+    /**
+     * Terminate the rendering thread.
+     */
+    fun terminate()
 }
 
 internal class GLDrawScopeImpl(
@@ -28,6 +33,12 @@ internal class GLDrawScopeImpl(
 ) : GLDrawScope {
     internal var redrawAfter: Duration? = (1000 / 60).milliseconds
         private set
+    internal var terminate = false
+        private set
+
+    override fun terminate() {
+        terminate = true
+    }
 
     override fun redrawAfter(duration: Duration?) {
         redrawAfter = duration

src/main/java/dev/silenium/compose/gl/surface/GLSurfaceView.kt

@@ -239,10 +239,13 @@ class GLSurfaceView internal constructor(
             val renderResult = fboPool!!.render(deltaTime.nanoseconds, drawBlock)
             val e = renderResult.exceptionOrNull()
             if (e is NoRenderFBOAvailable) {
-                logger.debug("No FBO available, waiting for the next frame")
-                sleep(1)
+                try {
+                    sleep(1)
+                } catch (e: InterruptedException) {
+                    break
+                }
                 continue
-            } else if (e is CancellationException) {
+            } else if (e is CancellationException || e is InterruptedException) {
                 break
             } else if (e != null) {
                 logger.error("Failed to render frame", e)

src/test/kotlin/Main.kt

@@ -12,12 +12,10 @@ import androidx.compose.runtime.*
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.graphics.TransformOrigin
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.window.ApplicationScope
 import androidx.compose.ui.window.Window
 import androidx.compose.ui.window.awaitApplication
-import dev.silenium.compose.gl.surface.FBOSizeOverride
 import dev.silenium.compose.gl.surface.GLSurfaceView
 import dev.silenium.compose.gl.surface.Stats
 import dev.silenium.compose.gl.surface.rememberGLSurfaceState
@@ -32,7 +30,7 @@ import kotlin.time.Duration.Companion.milliseconds
 @Preview
 fun ApplicationScope.App() {
     MaterialTheme {
-        Box(contentAlignment = Alignment.TopStart, modifier = Modifier.fillMaxSize().background(Color.Black)) {
+        Box(contentAlignment = Alignment.TopStart, modifier = Modifier.fillMaxSize().background(Color.White)) {
             val state = rememberGLSurfaceState()
             var targetHue by remember { mutableStateOf(0f) }
             val color by animateColorAsState(
@@ -58,10 +56,16 @@ fun ApplicationScope.App() {
                     .zoomable(rememberZoomableState(ZoomSpec(6f)))
                     .align(Alignment.Center),
                 presentMode = GLSurfaceView.PresentMode.MAILBOX,
-                fboSizeOverride = FBOSizeOverride(4096, 4096, TransformOrigin.Center),
+//                fboSizeOverride = FBOSizeOverride(4096, 4096, TransformOrigin.Center),
             ) {
                 glClearColor(color.red, color.green, color.blue, color.alpha)
                 glClear(GL_COLOR_BUFFER_BIT)
+                try {
+                    Thread.sleep(33, 333)
+                } catch (e: InterruptedException) {
+                    terminate()
+                    return@GLSurfaceView
+                }
                 glBegin(GL_QUADS)
                 glColor3f(1f, 0f, 0f)
                 glVertex2f(-1f, 0f)