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Fixed bug 2293 - Precise scrolling events

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Martijn Courteaux

I implemented precise scrolling events. I have been through all the folders in /src/video/[platform] to implement where possible. This works on OS X, but I can't speak for others. Build farm will figure that out, I guess. I think this patch should introduce precise scrolling on OS X, Wayland, Mir, Windows, Android, Nacl, Windows RT.

The way I provide precise scrolling events is by adding two float fields to the SDL_MouseWheelScrollEvent datastructure, called "preciseX" and "preciseY". The old integer fields "x" and "y" are still present. The idea is that every platform specific code normalises the scroll amounts and forwards them to the SDL_SendMouseWheel function. It is this function that will now accumulate these (using a static variable, as I have seen how it was implemented in the Windows specific code) and once we hit a unit size, set the traditional integer "x" and "y" fields.

I believe this is pretty solid way of doing it, although I'm not the expert here.

There is also a fix in the patch for a typo recently introduced, that might need to be taken away by the time anybody merges this in. There is also a file in Nacl which I have stripped a horrible amount of trailing whitespaces. (Leave that part out if you want).
This commit is contained in:
Sam Lantinga
2017-08-14 21:28:04 -07:00
parent 72b195d27c
commit a4cfa93670
10 changed files with 80 additions and 90 deletions
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31
src/events/SDL_mouse.c
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@@ -508,10 +508,11 @@ SDL_SendMouseButton(SDL_Window * window, SDL_MouseID mouseID, Uint8 state, Uint8
}
int
SDL_SendMouseWheel(SDL_Window * window, SDL_MouseID mouseID, int x, int y, SDL_MouseWheelDirection direction)
SDL_SendMouseWheel(SDL_Window * window, SDL_MouseID mouseID, float x, float y, SDL_MouseWheelDirection direction)
{
SDL_Mouse *mouse = SDL_GetMouse();
int posted;
int integral_x, integral_y;
if (window) {
SDL_SetMouseFocus(window);
@@ -521,6 +522,26 @@ SDL_SendMouseWheel(SDL_Window * window, SDL_MouseID mouseID, int x, int y, SDL_M
return 0;
}
mouse->accumulated_wheel_x += x;
if (mouse->accumulated_wheel_x > 0) {
integral_x = (int)SDL_floor(mouse->accumulated_wheel_x);
} else if (mouse->accumulated_wheel_x < 0) {
integral_x = (int)SDL_ceil(mouse->accumulated_wheel_x);
} else {
integral_x = 0;
}
mouse->accumulated_wheel_x -= integral_x;
mouse->accumulated_wheel_y += y;
if (mouse->accumulated_wheel_y > 0) {
integral_y = (int)SDL_floor(mouse->accumulated_wheel_y);
} else if (mouse->accumulated_wheel_y < 0) {
integral_y = (int)SDL_ceil(mouse->accumulated_wheel_y);
} else {
integral_y = 0;
}
mouse->accumulated_wheel_y -= integral_y;
/* Post the event, if desired */
posted = 0;
if (SDL_GetEventState(SDL_MOUSEWHEEL) == SDL_ENABLE) {
@@ -528,8 +549,12 @@ SDL_SendMouseWheel(SDL_Window * window, SDL_MouseID mouseID, int x, int y, SDL_M
event.type = SDL_MOUSEWHEEL;
event.wheel.windowID = mouse->focus ? mouse->focus->id : 0;
event.wheel.which = mouseID;
event.wheel.x = x;
event.wheel.y = y;
#if 0 /* Uncomment this when it goes in for SDL 2.1 */
event.wheel.preciseX = x;
event.wheel.preciseY = y;
#endif
event.wheel.x = integral_x;
event.wheel.y = integral_y;
event.wheel.direction = (Uint32)direction;
posted = (SDL_PushEvent(&event) > 0);
}