In my application I need to return the relative mouse position from an SDL_Surface, the problem is the mouse position that gets returned is relative to the SDL window and not the SDL_Surface. I guess my question is what is the easiest / most effective way of doing this. Any questions just ask. Thanks.
EDIT: Sorry I should have explained better, I have SDL_Surface* Surf_Display; on Surf_display there is an Image say its 1000 x 1000, So in order to see the image on a 600 x 600 window I have a camera that I can move around ( really its the surface that moves not the camera ) for instance to look right of the image I move the surface -1 left if that makes sense. So my problem is when I click my mouse on a part of the surface(image) my mouse returns the position that the mouse compared to where the cursor is in the window, what i'm wanting is so that it returns the position of the cursor compared to where it is on the surface(image)
I hope that better explains the situation. Thanks again
Just add(or subtract, depending on how you look at it) the offset to the mouse coordinates. So you're drawing the surface something like this:
SDL_Rect dest_rect = { -camera.x, -camera.y };
SDL_BlitSurface(image_surface, NULL, screen_surface, &dest_rect);
I don't know if you're using event based mouse handling, or if you're using SDL_GetMouseState, but either way, you would simply add camera.x and camera.y to the mouse position, for example:
int x, y;
SDL_GetMouseState(&x, &y);
x += camera.x;
y += camera.y;
Related
I want to get the current mouse position of the window, and assign it to 2 variables x and y (co-ordinates relative to the window, not to the screen as a whole).
I'm using Win32 and C++.
And a quick bonus question: how would you go about hiding the cursor/unhiding it?
You get the cursor position by calling GetCursorPos.
POINT p;
if (GetCursorPos(&p))
{
//cursor position now in p.x and p.y
}
This returns the cursor position relative to screen coordinates. Call ScreenToClient to map to window coordinates.
if (ScreenToClient(hwnd, &p))
{
//p.x and p.y are now relative to hwnd's client area
}
You hide and show the cursor with ShowCursor.
ShowCursor(FALSE);//hides the cursor
ShowCursor(TRUE);//shows it again
You must ensure that every call to hide the cursor is matched by one that shows it again.
GetCursorPos() will return to you the x/y if you pass in a pointer to a POINT structure.
Hiding the cursor can be done with ShowCursor().
I was wondering if anyone could help me with some code, essentially I've made a small function that moves the mouse cursor relative to the mouse cursor's current position, however the cursor teleports; I'd like to find a way to make it 'glide', smoothly so it looks a little more natural.
Here is the code below:
#import <Windows.h>
void MouseXY(int x, int y) {
POINT p;
if (GetCursorPos(&p)) {
SetCursorPos(p.x + x, p.y + y);
}
}
Any help would be greatly appreciated.
If you want the cursor to slide smoothly instead of teleporting, I would suggest using while loop, some delta value, and Sleep function...
What you are basically doing there is instantaneously moving the cursor.
What you probably want is to move the cursor with smaller steps.
I am trying to use the function mouseMove(int x, int y) to draw a circle centered at my mouse as I click and drag it across the screen. Circles will be drawn on the moving mouse like a spray paint. So far, this is what I have
void mouseMove(int x, int y) {
glBegin(GL_POLYGON);
for (int i = 0; i <= 360; i++)
{
float theta = (2 * 3.14 * i) / 360;
glVertex2f((size/2 + x) * cos(theta), (size/2 + y) * sin(theta));
}
glEnd();
glutPostRedisplay();
}
But when using this, it draws very large circles that aren't centered around my mouse. How would I alter this to make the program draw circles centered at my mouse?
To describe the project, I am creating a painting program that changes shapes, colors, sizes, and rotations of the drawing done in mouseMove. For now, the size is an int set to 32. When the user selects the shape using the 'b' key in a keyboard function, he/she can switch the shapes that are drawn around the mouse as the user clicks and drags the mouse around. Like a spray paint. All the other shapes work shaped around the mouse except for the circle shape spray.
This answer assumes that things like your viewport and projection matrices are set up correctly, and that the input to this function is taking into account the fact that "screen coordinates" (what the mouse uses) are not the same thing as "OpenGL Coordinate Space" (this usually implies reversing the direction of the y-axis for one or the other).
The math you're using for setting your vertex coordinates is wrong. The mouse's x and y coordinates should not be multiplied by the sine/cosine functions.
The correct way to write it is
glVertex2f((size/2) * cos(theta) + x, (size/2) * sin(theta) + y);
I would also add that you appear to still be using OpenGL's Immediate Mode rendering, which is Deprecated and will offer extremely poor training for a professional setting. I highly advise you learn Modern OpenGL (3.x+) and reapply those concepts to whatever projects you're already working on. This is a very good tutorial.
I am currently working on a project which requires me to know when the mouse is being dragged to the left, or to the right.
What I would like to do with this information, is drag an object in 3d space (with OpenGL/Win32), left, or right, depending on which way the mouse was dragged.
The problem is, I have no idea how to determine which way the mouse is being dragged.
I tried finding the previous x coordinate, and subtracting it from the current x coordinate, but I do not know how to determine the previous x coordinate!
Can someone please help me?
(P.S. I already know that the current x mouse location is found with LOWORD(lParam), but what I do not know is how to determine the previous x mouse location. Thanks for your time.)
You could do it yourself by storing the current mouse position as the 'last' mouse position, and then after two mouse position updates, subtract.
onMouseMove(mouseX, mouseY):
if previousX and previousY are set:
deltaX = previousX - mouseX
deltaY = previousY - mouseY
actOnDrag(deltaX, deltaY)
previousX = mouseX
previousY = mouseY
You could set previousX and previousY to some crazy sentinel value (e.g. -1) to determine whether they have ever been set.
You could use the DragDetect function.
BOOL DragDetect(HWND hwnd, POINT pt);
https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-dragdetect
I'm using GLUT and developing a FPS game. I need a way to trap the mouse so that the camera continues to move because right now when the mouse position exceeds the monitor limit, there is no way to calculate change in X or change in Y. How can I 'trap' the mouse with GLUT?
Thanks
I'd recommend using a ready-made engine like OGRE 3D instead, but if you really want to reinvent the wheel, here's how...
In all cases I'm aware of, PC FPS games "trap" the pointer by registering a mouse motion callback, noting the relative motion, and then warping the pointer back to the center of the window.
Here's some code I wrote to add mouse input to a sample ping-pong table in an OpenGL with C++ course a year or two ago:
void resetPointer() {
glutWarpPointer(TABLE_X/2, TABLE_Y/2);
lastMousePos = TABLE_Y/2;
}
void mouseFunc(int sx, int sy) {
if (!started) { return; }
int vertMotion = lastMousePos - sy;
lastMousePos = sy;
player1.move(vertMotion);
// Keep the pointer from leaving the window.
if (fabs(TABLE_X/2 - sx) > 25 || fabs(TABLE_Y/2 - sy) > 25) {
resetPointer();
}
}
// This goes in with your "start new game" code if you want a menu
resetPointer();
glutSetCursor(GLUT_CURSOR_NONE);
glutPassiveMotionFunc(mouseFunc);
It only tracks vertical motion, but adding horizontal is trivial.