Sensitivity: Handle sensitivities < 1.0 without rounding errors #111
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In particular, although emacs generally doesn't generate ~ backup files when working in a git tree, autoreconf does generate config.h.in~, which should be ignored. Signed-off-by: Ian Jackson <[email protected]>
In a moment, we are going to make the in-use representation of the sensitivity more complicated. We will need accessor methods for use by the configuration machinery. Provide these accessor methods now, to reduce noise in the substantive patch. For now they just access the single double. Rename the variable so that we catch all of the references. Signed-off-by: Ian Jackson <[email protected]>
Background: We tell the xf86 core that our x and y ranges are the overall range of the trackpad. The xf86 core scales the supplied values in the same way for relative and absolute pointers. The result is that at sensitivity 1.0, the scale of the whole trackpad corresponds to the scale of the whole screen (so for example moving the pointer from the very LHS to the very RHS of the screen can be achieved by moving a finger from the very LHS to the very RHS of the trackpad). On some modern machines the resolution of the screen is much higher than the resolution of the trackpad. When this occurs, due to rounding error, it can be impossible to reach the bottom and right edges of the screen. This is because even a 1-unit movement on the trackpad is multipled by a >1-pixel pointer movement, and pointer movements which would take the pointer off the screen are ignored. (Arguably this is some kind of bug.) In any case the user will probably want to be able to control the pointer position with 1-pixel accuracy. This requires mtrack to specify a higher resolution. Otherwise, the fact that the values provided by mtrack to xf86 are integers means that attempts to set the sensitivity to values < 1.0 are not properly effective - resulting in "lumpy" response. Fix this as follows: * Split sensitivity_val into sensitivity_big and _smalldiv, both >= 1.0, such that sensitivity_big/sensitivity_smalldiv is the specified sensitivity. * Multiply the size we tell xf86 by sensitivity_smalldiv. As a result, when sensitivity is < 1.0, instead of scaling down motions (resulting in unwanted rounding), we scale up the nominal size (resulting in a lower scaling factor being applied by xf86). When the sensitivity is > 1.0, everything behaves as before. There is no change to the visible configuration. Signed-off-by: Ian Jackson <[email protected]>
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Sensitivity: Handle sensitivities < 1.0 without rounding errors.
Including two preparatory patches.