gl_engine: fix memoty leak on target resize

We must to remove offscreen render buffers during removing render target

https://github.com/thorvg/thorvg/issues/3210

src/renderer/gl_engine/tvgGlRenderTarget.cpp

@@ -22,25 +22,18 @@
 
 #include "tvgGlRenderTarget.h"
 
-GlRenderTarget::GlRenderTarget(uint32_t width, uint32_t height): mWidth(width), mHeight(height) {}
+GlRenderTarget::GlRenderTarget() {}
 
 GlRenderTarget::~GlRenderTarget()
 {
-    if (mFbo == 0) return;
+    reset();
-    GL_CHECK(glBindFramebuffer(GL_FRAMEBUFFER, 0));
-    GL_CHECK(glDeleteFramebuffers(1, &mFbo));
-
-    if (mColorTex != 0) {
-        GL_CHECK(glDeleteTextures(1, &mColorTex));
-    }
-    if (mDepthStencilBuffer != 0) {
-        GL_CHECK(glDeleteRenderbuffers(1, &mDepthStencilBuffer));
-    }
 }
 
-void GlRenderTarget::init(GLint resolveId)
+void GlRenderTarget::init(uint32_t width, uint32_t height, GLint resolveId)
 {
-    if (mFbo != GL_INVALID_VALUE || mWidth == 0 || mHeight == 0) return;
+    if (mFbo != GL_INVALID_VALUE || width == 0 || height == 0) return;
+    mWidth = width;
+    mHeight = height;
 
     //TODO: fbo is used. maybe we can consider the direct rendering with resolveId as well.
     GL_CHECK(glGenFramebuffers(1, &mFbo));
@@ -82,6 +75,18 @@ void GlRenderTarget::init(GLint resolveId)
     GL_CHECK(glBindFramebuffer(GL_FRAMEBUFFER, resolveId));
 }
 
+void GlRenderTarget::reset()
+{
+    if (mFbo == 0) return;
+    GL_CHECK(glBindFramebuffer(GL_FRAMEBUFFER, 0));
+    GL_CHECK(glDeleteFramebuffers(1, &mFbo));
+    GL_CHECK(glDeleteRenderbuffers(1, &mColorBuffer));
+    GL_CHECK(glDeleteRenderbuffers(1, &mDepthStencilBuffer));
+    GL_CHECK(glDeleteFramebuffers(1, &mResolveFbo));
+    GL_CHECK(glDeleteTextures(1, &mColorTex));
+    mFbo = GL_INVALID_VALUE;
+}
+
 GlRenderTargetPool::GlRenderTargetPool(uint32_t maxWidth, uint32_t maxHeight): mMaxWidth(maxWidth), mMaxHeight(maxHeight), mPool() {}
 
 GlRenderTargetPool::~GlRenderTargetPool()
@@ -125,8 +130,8 @@ GlRenderTarget* GlRenderTargetPool::getRenderTarget(const RenderRegion& vp, GLui
         }
     }
 
-    auto rt = new GlRenderTarget(width, height);
+    auto rt = new GlRenderTarget();
-    rt->init(resolveId);
+    rt->init(width, height, resolveId);
     rt->setViewport(vp);
     mPool.push(rt);
     return rt;

src/renderer/gl_engine/tvgGlRenderTarget.h

@@ -28,11 +28,11 @@
 class GlRenderTarget
 {
 public:
-    GlRenderTarget() = default;
+    GlRenderTarget();
-    GlRenderTarget(uint32_t width, uint32_t height);
     ~GlRenderTarget();
 
-    void init(GLint resolveId);
+    void init(uint32_t width, uint32_t height, GLint resolveId);
+    void reset();
 
     GLuint getFboId() { return mFbo; }
     GLuint getResolveFboId() { return mResolveFbo; }

src/renderer/gl_engine/tvgGlRenderer.cpp

@@ -52,6 +52,8 @@ void GlRenderer::flush()
 {
     clearDisposes();
 
+    mRootTarget.reset();
+
     ARRAY_FOREACH(p, mComposePool) delete(*p);
     mComposePool.clear();
 
@@ -834,9 +836,8 @@ bool GlRenderer::target(void* context, int32_t id, uint32_t w, uint32_t h)
 
     currentContext();
 
-    mRootTarget = GlRenderTarget(surface.w, surface.h);
     mRootTarget.setViewport({0, 0, static_cast<int32_t>(surface.w), static_cast<int32_t>(surface.h)});
-    mRootTarget.init(mTargetFboId);
+    mRootTarget.init(surface.w, surface.h, mTargetFboId);
 
     return true;
 }