Thread: Windows GDI vs. Java Graphics

I never thought I'd be posting in this board, but...

I'm going to be writing some custom software (targeted for windows) which, among other things, needs to display graphs of large data-sets. My preference would be to write this in Java since it would be very quick and easy, however it's looking like some other parts of the app might need to be written in C or C++. This leaves me with two choices:

• Write the app in Java and integrate the C++ parts with JNI.
• Write the whole app in C++.

I'm leaning towards the first option, but I have some beefs with it that I won't bother explaining (not really relevent to the question).

My beef with number 2 brings me to the question in this thread. I know I can build everything very easily in Java, I'm not so sure about using GDI. I don't want to depend on uncommon libs like SDL or Allegro, and I don't want to the software to require things like OpenGL or DX. Thus leaves windows GDI.

Anyone have opinions on GDI for rendering something like a scrollable graph of a large dataset? Anyone have experience with both GDI and Java Graphics care to contrast the two?


(by graph here, i mean a 2D, x vs. y plot of data. By large i mean too big to render all at once, but small enough to fit into memory)

I also need to ability to have interactions with the graph, such as marking points, retreiving data from mouse clicks, etc...

It's possible, but quite awkward vs Java. I mean, with GDI you'd have to come up with all the bar drawing stuff yourself whereas in Java it's pretty much waiting to be declared. GDI+ gives you the option of some effects too but still it's a bit of an undertaking.

If you're more comfortable with Java, use it. Doing the JNI stuff shows that you're dead clever and can make different languages work together.

well, if you intend to display the entire graph in the window at once, you can just generate a BMP in memory then use StretchBlit to paint it to the DC. if the graph will be larger than the window, just create a window with scroll bar properties, then use BitBlit to render the image. Or you could just use the GDI drawing functions for makign the lines and points, btu I never realy bothered with those so I dont know how they perform.

Generating a BMP would make interacting with the graph awkward. I'm leaning even more to the Java side. Thanks for the replies.

Originally Posted by abachler

well, if you intend to display the entire graph in the window at once, you can just generate a BMP in memory then use StretchBlit to paint it to the DC. if the graph will be larger than the window, just create a window with scroll bar properties, then use BitBlit to render the image. Or you could just use the GDI drawing functions for makign the lines and points, btu I never realy bothered with those so I dont know how they perform.

• It's BitBlt and StretchBlt, not "Blit" ;P
• Generating a bitmap of something complex and then stretching it will give you dreadful results. But this doesn't mean that GDI is crap and does not have an appropriate way to do this.
  
  What you can do is create a metafile. This is just as easy as creating a bitmap to draw on, but it stores not pixels but vector graphics (the drawing commands). You can then draw it to your window using any dimensions, Windows will just execute the drawing commands you compiled. I'm quite sure Java doesn't have such a functionality.

whether the BMP is simple or complex is irrelevant, but stretchblt does technically run a bit slower than bitblt. Then again if your rendering thread is the cpu hog in your app I assume you would switch to DirectX

Originally Posted by abachler

whether the BMP is simple or complex is irrelevant, but stretchblt does technically run a bit slower than bitblt.

Was that a reply to my statement? What do you mean by that? I guess you don't get my point at all.