Added OpenGL (Windows).

samples/SkijaInjectSample/src/main/kotlin/SkijaInjectSample/App.kt

@@ -15,6 +15,7 @@ import kotlin.math.cos
 import kotlin.math.sin
 
 fun main(args: Array<String>) {
+    System.setProperty("skiko.renderApi", "OPENGL")
     repeat(1) {
         createWindow("window $it")
     }
@@ -90,31 +91,26 @@ class Renderer(
     var canvas: Canvas? = null
 
     override fun onRender(canvas: Canvas, width: Int, height: Int, nanoTime: Long) {
-        // this.canvas = canvas
-        // val contentScale = layer.contentScale
-        // canvas.scale(contentScale, contentScale)
-        // displayScene(this, (width / contentScale).toInt(), (height / contentScale).toInt(), nanoTime)
-        // layer.needRedraw()
-
-//////////////////////////////////////////////////
+        this.canvas = canvas
+        val contentScale = layer.contentScale
+        canvas.scale(contentScale, contentScale)
+        displayScene(this, (width / contentScale).toInt(), (height / contentScale).toInt(), nanoTime)
+
+        // Alpha layers test
+        val rectW = 100f
+        val rectH = 100f
+        val left = (width - rectW) / 2f
+        val top = (height - rectH) / 2f
         val pictureRecorder = PictureRecorder()
         val pictureCanvas = pictureRecorder.beginRecording(
-            Rect.makeLTRB(
-                0f,
-                0f,
-                100f,
-                100f
-            )
+            Rect.makeLTRB(left, top, left + rectW, top + rectH)
         )
-        pictureCanvas.drawLine(0f, 0f, 100f, 100f, Paint())
+        pictureCanvas.drawLine(left, top, left + rectW, top + rectH, Paint())
         val picture = pictureRecorder.finishRecordingAsPicture()
-        canvas.drawPicture(
-            picture,
-            null,
-            Paint() // if we replace it by null, everything will be normal
-        )
-        canvas.drawLine(100f, 0f, 0f, 100f, Paint())
-//////////////////////////////////////////////////
+        canvas.drawPicture(picture, null, Paint())
+        canvas.drawLine(left, top + rectH, left + rectW, top, Paint())
+
+        layer.needRedraw()
     }
 }
 

skiko/src/jvmMain/kotlin/org/jetbrains/skiko/context/OpenGLContextHandler.kt

@@ -26,13 +26,24 @@ internal class OpenGLContextHandler(layer: SkiaLayer) : ContextHandler(layer) {
         return true
     }
 
-    override fun initCanvas() {
-        disposeCanvas()
+    private var currentWidth = 0
+    private var currentHeight = 0
+    private fun isSizeChanged(width: Int, height: Int): Boolean {
+        if (width != currentWidth || height != currentHeight) {
+            currentWidth = width
+            currentHeight = height
+            return true
+        }
+        return false
+    }
 
+    override fun initCanvas() {
         val scale = layer.contentScale
         val w = (layer.width * scale).toInt().coerceAtLeast(0)
         val h = (layer.height * scale).toInt().coerceAtLeast(0)
 
+        if (isSizeChanged(w, h)) {
+            disposeCanvas()
             val gl = OpenGLApi.instance
             val fbId = gl.glGetIntegerv(gl.GL_DRAW_FRAMEBUFFER_BINDING)
             renderTarget = makeGLRenderTarget(
@@ -43,7 +54,6 @@ internal class OpenGLContextHandler(layer: SkiaLayer) : ContextHandler(layer) {
                 fbId,
                 FramebufferFormat.GR_GL_RGBA8
             )
-
             surface = Surface.makeFromBackendRenderTarget(
                 context!!,
                 renderTarget!!,
@@ -51,6 +61,7 @@ internal class OpenGLContextHandler(layer: SkiaLayer) : ContextHandler(layer) {
                 SurfaceColorFormat.RGBA_8888,
                 ColorSpace.getSRGB()
             )
+        }
 
         canvas = surface!!.canvas
     }