On Tue, Mar 22, 2011 at 17:18, Anthony Walter <sys...@gmail.com> wrote: > For drawing lines, shapes, fills, on Linux I'd recommend using cairo. On > Windows I'd say you should use GDI or GDI+. You can find pascal files > importing the functions for those libraries using google. Some of them may > come with FPC. > > For widgets, if you are using Lazarus, it comes with a widget toolkit. Then > there is also the free pascal gui tookit located here: > http://fpgui.sourceforge.net/ > > Finally, for handling scrolling, what you need to do is determine the max > bounds of your area, compare that to screen area and your drawing scale > (your zoom factor). Use that to recalculate both the horizontal and > vertical scroll bar information (page size, scroll size) when the draw area > is resized and update the scroll bars accordingly. > > When you receive a scroll position change notification (the user drags the > scroll bar) you call some api to scroll the drawing (such as > ScrollWindowEx), which will invalidate a dirty rectangle in your window. > > When you receive a paint notification (either when the user scrolls or a > window is dragged over your window), you should also retrieve the dirty > rectangle. Then you need to find the rectangles of your drawn objects that > intersect the dirty rectangle. Redraw objects that intersect the dirty > rectangle. > > If the user zooms in or out, invalidate the entire area. > > It's all pretty standard stuff ... > http://imagebot.org/snapshops/phun-gears-builder.jpg
Thanks Anthony for your answers. I will keep in mind these suggestions if I fail to find a higher-level component. (for example, the TAChart is a "higher-level" component for drawing charts that is much more convenient to use compared to drawing the chart from scratch). Ideally, I am hoping that already exists some kind of "svg canvas" that can be used in fpgui or Lazarus applications. For example: if I draw a rectangle in the canvas I want to be able to later : - change color - modify size/position - associate it with a "mouse click" event I didn't mention that I will need to handle in parallel multiple coordinates systems: - number of meters - position withing each track segment (each segment has a starting km and an ending km). And it's possible that a segment ends at km=35.4 and the next one begins at km=38.2 . It is even possible that the next segment has coordinates in reverse order. - position relative to balises So the problem itself is relatively mind-twisting . It would be really nice to find a component that allows me to add and manipulate the graphical objects in a "scalar-graphics" way , that takes care of drawing on-screen without forcing me to go into the details . -- Adrian _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
