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SImple GUI

Started by C0UNT Z3R0 Apr 20, 2004 at 10:40 AM 1 replies 600+ views

Original Post

Apr 20, 2004 at 10:40 AM

Hi all, Ive got a program im working on almost done and at the moment its a console app. I want to make a really simple GUI for it. I have made a psp image for this. What I need it: - Just one screen with my psp image on - Be able to use the mouse, click the buttons on the image and have them run my commands (instead of space bar) - Have the buttons change when pressed Thats it I think. I can get the one screen by using one side of a square and putting it right next to the screen but not sure this is the best way. I heard its best to Ortho mode but have no idea how to use it even after looking a a couple of tutorials. The mouse is the other thing, is there anyway of doing seeing where it is pixel by pixel (not sure if this would work corrected though or be accurate). I am surprised that no one had made a simple tutorial to do this being as it must be a question is asked quite alot. Maybe there is one that I dont know about!

Well if anyone can help let me know please Thanks

Kurioes

Apr 20, 2004 at 4:11 PM

Drawing GUIs is usually done by drawing textured rectangular polygons (quads) to the screen (as you said). glOrtho sets the projection matrix to a 2d projection. The projection matrix basically contains the perspective transformation, but since a GUI has no perspective (generally) glOrtho "removes" it.

You could use it like this;


glMatrixMode(GL_PROJECTION);
glOrtho(0.0f, 4.0f, 0.0f, 3.0f, 0.0f, 1.0f);
glMatrixMode(GL_MODELVIEW);

// draw rectangular textured quads here
glBegin(GL_QUADS);
    glTexCoord2f(tc1, tc2);
    glVertex2f(x, y);
    // etc...
glEnd();

The x coordinate goes from 0 (left) to 4 (right), the y coordinate goes from 0 (bottom) to top (3).

I included a glOrtho description for reference:


=======================================
The glOrtho function multiplies the current matrix by an orthographic matrix.

void glOrtho(

    GLdouble left, 	
    GLdouble right, 	
    GLdouble bottom, 	
    GLdouble top, 	
    GLdouble near, 	
    GLdouble far 	
   );	
 

Parameters

left, right

The coordinates for the left and right vertical clipping planes. 

bottom, top

The coordinates for the bottom and top horizontal clipping planes. 

near, far

The distances to the nearer and farther depth clipping planes. These distances are negative if the plane is to be behind the viewer.
=======================================

I hope this helps

EDIT: I missed the mouse part

You need to get a hold of the mouse coordinates. There are various ways to do so and many are platform dependent. I'll assume Windows.

In the windows messaging loop, the giant switch statements, add this (make sure there are two global ints in your program called xPos and yPos):


case WM_MOUSEMOVE:
    // the mouse has moved; windows is telling you where to.
    // this is in screen coordinates (pixels of window), counted from the upper left
    xPos = LOWORD(lParam);  // horizontal position of cursor 
    yPos = HIWORD(lParam);  // vertical position of cursor 
    break;

case WM_LBUTTONUP:
case WM_RBUTTONUP:
    // the user clicked at (xPos, yPos)
    xPos = LOWORD(lParam);  // horizontal position of cursor 
    yPos = HIWORD(lParam);  // vertical position of cursor 
    // check which button got clicked
    break;

Just determine whether the user clicked on a botton or not... you should be able to continue from here. I suggest looking up the windows documentation on the above windows messages.

[ Galactic Conquest | Bananas | My dead site | www.sgi.com | Goegel ]

[edited by - Kurioes on April 20, 2004 5:19:26 PM]

C0UNT Z3R0

Apr 25, 2004 at 6:04 AM

Cheers that was great, Got it all sorted now and it works great!

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