C Windows API: Polygon accept mouse input

Question

Say I create a polygon with the Polygon function, and i'd like it to accept input from the mouse (similar to a button).

How would I do that?

EDIT:
Processing the WM_LBUTTONDOWN and WM_MOUSEMOVE messages, I'm using this code to check if the mouse is in the area of the polygon:

if (LOWORD(lParam) < 375 && LOWORD(lParam) > 340 &&
    HIWORD(lParam) < 200 && HIWORD(lParam) > 90)

Problem is, the polygon is not a rectangle, its a polygon. So how would I go about detecting if the mouse was in the polygon only?

EDIT 2: I should also note, its only a triangle lol. Hope that makes this simpler.

That's often known as a triangle! ;-) Pretty easy to work out a hit test for that. I bet one of the sides is horizontal or vertical. — David Heffernan, Sep 28 '11 at 21:48
fully general polygon testing covered here: http://stackoverflow.com/questions/217578/point-in-polygon-aka-hit-test — David Heffernan, Sep 28 '11 at 22:07
This is covered pretty well in Windows with the GraphicsPath::IsVisible() function. That's however a C++ method, getting fancy in C is not that well supported. — Hans Passant, Sep 28 '11 at 23:01

score 0 · Accepted Answer · answered Sep 28 '11 at 21:14

0

Polygon() is a function that is used to draw to a device context. As such it cannot receive inupt. You need a windowed control to do that.

Handle the input in your window and use a hit test to check if you are inside the polygon.

answered Sep 28 '11 at 21:14

David Heffernan

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One way to do this is to create a path from the polygon, convert the path to a region, and then use PtInRegion. – Raymond Chen Sep 28 '11 at 22:01
@raymond indeed, but perhaps overkill for a triangle!! – David Heffernan Sep 28 '11 at 22:04

score 0 · Answer 2 · answered Sep 28 '11 at 21:15

A polygon can't accept input, it must be done through the window that the polygon was drawn on. Listen for the WM_LBUTTONDOWN message and look at the coordinates delivered with the message; determine if the coordinate is within the polygon or not. The easiest way to do that might be to draw the polygon on a bitmap the same size as the window, and test the point on the bitmap to see if it is the polygon color or not.

C Windows API: Polygon accept mouse input

2 Answers2