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win32: convert WM_MOUSEWHEEL position to client coordinates #4

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win32: convert WM_MOUSEWHEEL position to client coordinates #4

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17 changes: 15 additions & 2 deletions src/apprt/win32/App.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,7 @@ const COPYDATASTRUCT = sys.COPYDATASTRUCT;

// Additional externs not in sys.zig
extern "user32" fn ClientToScreen(hWnd: HWND, lpPoint: *POINT) callconv(.winapi) BOOL;
extern "user32" fn ScreenToClient(hWnd: HWND, lpPoint: *POINT) callconv(.winapi) BOOL;
extern "user32" fn SetForegroundWindow(hWnd: HWND) callconv(.winapi) BOOL;
extern "user32" fn GetWindowTextW(hWnd: HWND, lpString: [*]u16, nMaxCount: c_int) callconv(.winapi) c_int;
extern "user32" fn SetCapture(hWnd: HWND) callconv(.winapi) ?HWND;
Expand Down Expand Up @@ -1749,9 +1750,21 @@ pub fn surfaceDispatch(app: *App, surface: *Surface, hwnd: HWND, msg: UINT, wpar
},
0x020A => {
if (surface.core_surface) |core| {
// Unlike WM_MOUSEMOVE and the button messages, WM_MOUSEWHEEL
// carries the pointer position in *screen* coordinates, so it
// has to be converted before it can be used as a surface
// position. Without this, mouse reporting silently drops every
// wheel event whenever the window is positioned such that the
// screen coordinates fall outside the surface (see
// mouse_encode.posOutOfViewport).
var pt: POINT = .{
.x = @as(i16, @truncate(lparam & 0xFFFF)),
.y = @as(i16, @truncate((lparam >> 16) & 0xFFFF)),
};
_ = ScreenToClient(hwnd, &pt);
surface.cursor_pos = .{
.x = @floatFromInt(@as(i16, @truncate(lparam & 0xFFFF))),
.y = @floatFromInt(@as(i16, @truncate((lparam >> 16) & 0xFFFF))),
.x = @floatFromInt(pt.x),
.y = @floatFromInt(pt.y),
};
const delta: i16 = @truncate(@as(isize, @bitCast(wparam)) >> 16);
const yoff: f64 = @as(f64, @floatFromInt(delta)) / 120.0;
Expand Down