I found that the failing corner in native macOS window tiling changes with the Dock position. With the Dock on the right, the upper-right corner produces the right half instead of a quarter. With the Dock on the left, the upper-left corner produces the left half instead of a quarter. With the Dock at the bottom, all four corners produce quarters. Apple's macOS Tahoe guide describes dragging to any corner as a way to tile a window there.
Configuration
- Mac mini
Mac14,12, Apple M2 Pro - macOS Tahoe 26.7 (
25G229) - One external iiyama PL4071UH (ProLite X4071UHSU) display, with a [native panel resolution of
3840 × 2160]; no adjacent display and mirroring off. A3840 × 2160mode is available in macOS, but it was not the mode used for these measurements. - Active macOS display mode reported by
CGDisplayModeand System Information:3008 × 1692pixels at 60 Hz; the interface “looks like”1504 × 846points (2× backing scale). This is a scaled configuration on the 4K display. NSScreen.frame:1504 × 846points.NSScreen.visibleFramewith the Dock on the right: approximately1456 × 816points (about 48 points removed at the right for the Dock and 30 at the top for the menu bar).- macOS reports
Television: Yesfor this display and exposes an Underscan control in Displays settings. The slider appeared at the “No” end during inspection; its effect on this tiling behavior has not been tested. - Dock position changed between right, left, and bottom for the comparison below
- Dock auto-hide is currently off (
com.apple.dock autohide = 0) - Native drag-to-edge tiling and the Option-key tiling accelerator enabled; tiled window margins disabled
- Upper-right Hot Corner configured without a modifier key during the right-Dock measurement
Steps to reproduce
- Open a blank, resizable TextEdit window and enable native drag-to-edge tiling.
- Set the Dock position to Right in System Settings → Desktop & Dock. Drag the window by its title bar to each screen corner and release after the tiling preview appears.
- Set the Dock position to Left and repeat.
- Set the Dock position to Bottom and repeat.
Dock-position comparison
Dock position Upper-left corner Upper-right corner Lower corners
Right quarter right half quarters
Left left half quarter quarters
Bottom quarter quarter quarters
The left- and bottom-Dock comparisons are direct user observations. The right-Dock case was also measured programmatically as described below. This pattern points to a side-Dock interaction with detection of the adjacent upper corner; the internal cause is not yet established.
The display's scaled mode and its classification as a television are additional variables worth recording. Neither has been isolated as a cause: the controlled change so far is the Dock position. A useful follow-up would be to repeat the same corner tests at another display mode, including 3840 × 2160, with the Dock kept on the same side, and to record the Underscan setting.
Instrumented result with Dock on the right
I sampled NSEvent.mouseLocation every 20 ms, used CGEventSource.buttonState to identify the release, and read the window bounds using CGWindowListCopyWindowInfo about 0.6 seconds later. The same TextEdit window ID was observed for all four corner tests. Pointer and window coordinates below use the top-left of the display as (0, 0); dimensions are in macOS points.
Release corner Pointer (x, y) Window (x, y, width, height) Result
Top left (0, 0) (-1, 30, 727, 409) quarter
Top right (1503.98, 0) (727, 30, 728, 816) RIGHT HALF
Bottom left (0, 845.98) (-1, 438, 727, 409) quarter
Bottom right (1503.98, 845.98) (727, 438, 728, 409) quarter
At the upper-right release, the pointer is effectively at the screen's rightmost x coordinate and at y = 0. The resulting window is 816 points high, compared with 409 points for each quarter tile. The Hot Corner did not prevent the pointer from reaching that coordinate.
Expected result
Dragging to any of the four corners should produce the corresponding quarter regardless of whether the Dock is on the right, left, or bottom.