Improve commentary in xterm.c
* src/xterm.c (xi_populate_device_from_info, xi_handle_new_classes) (syms_of_xterm): Improve commentary on touch events.
This commit is contained in:
Po Lu
parent
a4087f5955
commit
8b1c92da79
1 changed files with 79 additions and 16 deletions
95
src/xterm.c
95
src/xterm.c
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@ -5497,12 +5497,24 @@ xi_populate_device_from_info (struct x_display_info *dpyinfo,
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no input.
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The device attachment is a device ID whose meaning varies
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depending on the device use. If the device is a master device,
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then the attachment is the device ID of the other device in its
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seat (the master keyboard for master pointer devices, and vice
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versa). Otherwise, it is the ID of the master device the slave
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depending on the device's use. If a device is a master device,
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then its attachment is the device ID of the other device in its
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seat (the master keyboard for master pointer devices and vice
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versa.) Otherwise, it is the ID of the master device the slave
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device is attached to. For slave devices not attached to any
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seat, its value is undefined. */
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seat, its value is undefined.
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Emacs receives ordinary pointer and keyboard events from the
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master devices associated with each seat, discarding events from
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slave devices. However, multiplexing events from touch devices
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onto a master device poses problems: if both dependent and direct
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touch devices are attached to the same master pointer device, the
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coordinate space of touch events sent from that seat becomes
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ambiguous. In addition, the X server does not send TouchEnd
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events to cancel ongoing touch sequences if the slave device that
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is their source is detached. As a result of these ambiguities,
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touch events are processed from and recorded onto their slave
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devices instead. */
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xi_device->device_id = device->deviceid;
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xi_device->grab = 0;
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@ -5516,7 +5528,7 @@ xi_populate_device_from_info (struct x_display_info *dpyinfo,
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#ifdef HAVE_XINPUT2_2
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xi_device->touchpoints = NULL;
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xi_device->direct_p = false;
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#endif
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#endif /* HAVE_XINPUT2_1 */
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#ifdef HAVE_XINPUT2_1
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if (!dpyinfo->xi2_version)
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@ -5582,9 +5594,34 @@ xi_populate_device_from_info (struct x_display_info *dpyinfo,
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case XITouchClass:
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{
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touch_info = (XITouchClassInfo *) device->classes[c];
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xi_device->direct_p = touch_info->mode == XIDirectTouch;
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/* touch_info->mode indicates the coordinate space that
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this device reports in its touch events.
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DirectTouch means that the device uses a coordinate
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space that corresponds to locations on the screen. It
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is set by touch screen devices which are overlaid
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over the raster itself.
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The other value (DependentTouch) means that the device
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uses a separate abstract coordinate space corresponding
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to its own surface. Emacs ignores events from these
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devices because it does not support recognizing touch
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gestures from surfaces other than the screen.
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Master devices may report multiple touch classes for
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attached slave devices, leaving the nature of touch
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events they send ambiguous. The problem of
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discriminating between these events is bypassed
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entirely through only processing touch events from the
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slave devices where they originate. */
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if (touch_info->mode == XIDirectTouch)
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xi_device->direct_p = true;
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else
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xi_device->direct_p = false;
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}
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#endif
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#endif /* HAVE_XINPUT2_2 */
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default:
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break;
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}
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@ -5611,7 +5648,7 @@ xi_populate_device_from_info (struct x_display_info *dpyinfo,
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}
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SAFE_FREE ();
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#endif
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#endif /* HAVE_XINPUT2_1 */
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}
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/* Populate our client-side record of all devices, which includes
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@ -13443,7 +13480,7 @@ xi_handle_new_classes (struct x_display_info *dpyinfo, struct xi_device_t *devic
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device->scroll_valuator_count = 0;
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#ifdef HAVE_XINPUT2_2
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device->direct_p = false;
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#endif
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#endif /* HAVE_XINPUT2_2 */
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for (i = 0; i < num_classes; ++i)
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{
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@ -13461,10 +13498,34 @@ xi_handle_new_classes (struct x_display_info *dpyinfo, struct xi_device_t *devic
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case XITouchClass:
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touch = (XITouchClassInfo *) classes[i];
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/* touch_info->mode indicates the coordinate space that this
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device reports in its touch events.
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DirectTouch means that the device uses a coordinate space
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that corresponds to locations on the screen. It is set
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by touch screen devices which are overlaid over the
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raster itself.
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The other value (DependentTouch) means that the device
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uses a separate abstract coordinate space corresponding
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to its own surface. Emacs ignores events from these
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devices because it does not support recognizing touch
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gestures from surfaces other than the screen.
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Master devices may report multiple touch classes for
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attached slave devices, leaving the nature of touch
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events they send ambiguous. The problem of
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discriminating between these events is bypassed entirely
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through only processing touch events from the slave
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devices where they originate. */
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if (touch->mode == XIDirectTouch)
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device->direct_p = true;
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else
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device->direct_p = false;
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break;
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#endif
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#endif /* HAVE_XINPUT2_2 */
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}
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}
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@ -13502,7 +13563,7 @@ xi_handle_new_classes (struct x_display_info *dpyinfo, struct xi_device_t *devic
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}
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}
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#endif
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#endif /* HAVE_XINPUT2_1 */
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/* Handle EVENT, a DeviceChanged event. Look up the device that
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changed, and update its information with the data in EVENT. */
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@ -32189,10 +32250,12 @@ reported as iconified. */);
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DEFVAR_BOOL ("x-input-grab-touch-events", x_input_grab_touch_events,
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doc: /* Non-nil means to actively grab touch events.
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This means touch sequences that started on an Emacs frame will
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reliably continue to receive updates even if the finger moves off the
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frame, but may cause crashes with some window managers and/or external
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programs. */);
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This means touch sequences that are obtained through a passive grab on
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an Emacs frame (or a parent window of such a frame) will reliably
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continue to receive updates, but may cause crashes with some window
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managers and/or external programs. Changing this option is only
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useful when other programs are making their own X requests pertaining
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to the window hierarchy of an Emacs frame. */);
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x_input_grab_touch_events = true;
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DEFVAR_BOOL ("x-dnd-fix-motif-leave", x_dnd_fix_motif_leave,
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