Libgdx Rendering Bitmap font to pixmap texture causes extremely slow rendering - libgdx

Question

I'm using libgdx scene2d to render 2d actors. Some of these actors originally included scene2d Label actors for rendering static text. The Labels work fine but drawing ~20 of them on the screen at once drops the frame rate by 10-15 frames, resulting in noticeably poor rendering while dragging.
I'm attempting to avoid the Labels by pre-drawing the text to textures, and rendering the textures as scene2d Image actors. I'm creating the texture using the code below:
BitmapFont font = manager.get(baseNameFont,BitmapFont.class);
GlyphLayout gl = new GlyphLayout(font,"Test Text");
int textWidth = (int)gl.width;
int textHeight = (int)gl.height;
LOGGER.info("textHeight: {}",textHeight);
//int width = Gdx.graphics.getWidth();
int width = textWidth;
//int height = 500;
int height = textHeight;
SpriteBatch spriteBatch = new SpriteBatch();
FrameBuffer m_fbo = new FrameBuffer(Pixmap.Format.RGB565, width,height, false);
m_fbo.begin();
Gdx.gl.glClearColor(1f,1f,1f,0f);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
Matrix4 normalProjection = new Matrix4()
.setToOrtho2D(0, 0, width, height);
spriteBatch.setProjectionMatrix(normalProjection);
spriteBatch.begin();
font.draw(spriteBatch,gl,0,height);
spriteBatch.end();//finish write to buffer
Pixmap pm = ScreenUtils.getFrameBufferPixmap(0, 0, (int) width, (int) height);//write frame buffer to Pixmap
m_fbo.end();
m_fbo.dispose();
m_fbo = null;
spriteBatch.dispose();
Texture texture = new Texture(pm);
textTexture = new TextureRegion(texture);
textTexture.flip(false,true);
manager.add(texture);
I assumed, and have read, that textures are often faster. However when I replaced the Labels with the texture, it had the same, if not worse, affect on the frame rate. Oddly, I'm not experiencing this when adding textures from a file, which makes me think I'm doing something wrong in my code. Is there a different way I should be pre-rendering these pieces of text?

Answer 1

I have not tested this, but I think you can enable culling for the whole Stage by setting its root view to use a cullingArea matching the world width and height of the viewport. I would do this in resize after updating the Stage Viewport just in case the update affects the world width and height of the viewport.
#Override
public void resize(int width, int height) {
//...
stage.getViewport().update(width, height, true);
stage.getRoot().setCullingArea(
new Rectangle(0f, 0f, stage.getViewport().getWorldWidth(), stage.getViewport().getWorldHeight())
);
}
It will only be able to cull Actors that have their x, y, width, and height set properly. This is true I think of anything in the scene2d UI package, but for your own custom Actors you will need to do it yourself.
If a child of your root view is a Group that encompasses more than the screen and many actors, you might want to cull its children, too, such that even if the group as a whole is not culled by the root view, the group can still cull a portion of its own children. To figure out the culling rectangle for this, I think you would intersect a rectangle of the group's size with the viewport's world size rectangle offset by -x and -y of the group's position (since the culling rectangle is relative to the position of the group it's set on).