Example how to clip using current matrix in 2D?

OpenGL OpenGL: Basic Coding
1

Hi, when there is a 2D OpenGL app with code like this:

glTranslated(100,0,0);
draw_something_with_polygons();

glTranslated(200,0,0);
draw_something_with_polygons();

and that displays some group of polygons (like a sprite) at one place and another place, how can you each time clip the same portion of that group?
E.g. clip away a few pixels starting on the left side.

glTranslated(100,0,0);
clip_first_10_pixels_of_that_something_starting_from_left();
draw_something_with_polygons();

glTranslated(200,0,0);
clip_first_10_pixels_of_that_something_starting_from_left();
draw_something_with_polygons();

I tried it with a scissor test but couldn’t get the correct window-space coordinates for it. I can get it to work with absolute window-space coordinates, but knowing where in the window space the next polygons will go is too hard for me. I tried to get the current projection matrix, transform the 2D point 0,0 with that matrix, and I thought that would be where the drawing takes place, but I got wrong numbers.

Is there any example of something like that?

2

I have found gluProject, with that it works. I had tried that myself, that is why it became too complicated.