CODEWITHSUNDEEP
csdl
Charles Leroy
Charles Leroy

Reputation: 13

SDL Relative Position

I have a theoretical question about SDL' Surface cursor. If I want to display surface_A on my screen I'll use a cursor created with SDL_Rect cursor; and I'll use it with SDL_BlitSurface();. The cursor will contain a position relative to the top-left corner of my window.

But if I want to display surface_B inside surface_A, do I have to indicate a cursor relative the top-left corner of my window or the top-left corner of surface_A ?

Upvotes: 0

Views: 2713

Answers (1)

ryyker
ryyker

Reputation: 23226

You may be making some wrong assumptions about the relative positions of your cursors. There is a very good, and detailed set of tutorials at the linked location that may clear things up for you...

From HERE...

Using the first tutorial as our base, we'll delve more into the world of SDL surfaces. As I attempted to explain in the last lesson, SDL Surfaces are basically images stored in memory. Imagine we have a blank 320x240 pixel surface. Illustrating the SDL coordinate system, we have something like this:

enter image description here

This coordinate system is quite different than the normal one you are familiar with. Notice how the Y coordinate increases going down, and the X coordinate increases going right. Understanding the SDL coordinate system is important in order to properly draw images on the screen.

Some additional terms that may help clarify:

SDL Window : You can think of this as physical pixels, or your monitor.
SDL Renderer : Controls the properties/settings of what is created in that window.

Upvotes: 1

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