I was wondering what the best way to draw an image part way outside the screen is? I'd like to do this in order to display only a section of the image to fill in gaps in my isometric engine. I notice when I call al_draw_bitmap with a dx/dy less than zero nothing is displayed even if part of the image should still be visible.

Example of what I am trying to achieve:

http://imgur.com/hUyUk

Can you show the code?

Screenshots of my test app showing the problem:

http://imgur.com/9rodW

I've wrapped up Allegro into a game library, but drawing the image boils down to one call:

al_draw_bitmap( pImage, nXPositionPx, nYPx, nFlags );

I would do something like this (lets say you don't know the size of the bitmap, but it get the -150;-150 coordinate (and the bitmap is bigger then 150x150 of course)):

I haven't tried it, but it should work

Not exactly related, but seeing as you're playing with isometric stuff here's something you might find interesting...

http://www.servo7.co.uk/iso/masking.aspx

You shouldn't need to chop the image at all, it should display as you would expect. Are you sure you're not using unsigned int for X and Y

<obvious>Are you really calling al_draw_bitmap directly? I.e. you don't have a condition somewhere that prevents bitmaps with negative values to be drawn? Apply palm to face, if applicable.</obvious>