切割sf :: Text，sf :: Texture等零件？

Question

I'm creating a simple chat client and server and I'm having some issues with how sf::Text is rendered. Say in the chat history for example. When users type their messages, the old messages will be pushed up. Eventually the message hits the top and I'll want to only display the part of the message that is still within the chat history. This is where I'm lost.

The element containing the text has two visible objects - sf::RectangleShape (the background for the text) and a sf::Text. I can easily adjust the size of the shape once it hits the top so it's not visible outside the chat history, but I can't adjust the size of the text without distorting the contents. Changing the character size obviously isn't ideal either.

What I want is to cut the text in half horizontally if half of the text is outside the chat history. My first thought was to mask it somehow but it seems like SFML has no support for that.

The reason I'm mentioning sf::Texture in the title as well is because I've had the same issue with that in the past. I just couldn't find a way to cut off parts of it, I only managed to distort it.

Is this possible at all in SFML?

Answer 1

One way of doing this is to draw the chat history to a sf::RenderTexture , which is the tool used for off-screen rendering.

Once you've drawn the chat history to your render texture, you can draw the texture on to the screen.

So if you place text that is half on the render texture and half outside, only the part that actually fits on there will be drawn.

Be aware though that render_texture are fairly expensive to construct, so you you want to re-use them and not create new ones all the time.