jlj-qmk/docs/feature_pointing_device.md
2017-12-09 10:46:11 -05:00

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## Pointing Device
Pointing Device is a generic name for a feature intended to be generic: moving the system pointer around. There are certainly other options for it - like mousekeys - but this aims to be easily modifiable and lightweight. You can implement custom keys to control functionality, or you can gather information from other peripherals and insert it directly here - let QMK handle the processing for you.
To enable Pointing Device, uncomment the following line in your rules.mk:
```
POINTING_DEVICE_ENABLE = yes
```
To manipulate the mouse report, you can use the following functions:
* `pointing_device_get_report()` - Returns the current report_mouse_t that represents the information sent to the host computer
* `pointing_device_set_report(report_mouse_t newMouseReport)` - Overrides and saves the report_mouse_t to be sent to the host computer
Keep in mind that a report_mouse_t (here "mouseReport") has the following properties:
* `mouseReport.x` - this is a signed int from -127 to 127 (not 128, this is defined in USB HID spec) representing movement (+ to the right, - to the left) on the x axis.
* `mouseReport.y` - this is a signed int from -127 to 127 (not 128, this is defined in USB HID spec) representing movement (+ upward, - downward) on the y axis.
* `mouseReport.v` - this is a signed int from -127 to 127 (not 128, this is defined in USB HID spec) representing vertical scrolling (+ upward, - downward).
* `mouseReport.h` - this is a signed int from -127 to 127 (not 128, this is defined in USB HID spec) representing horizontal scrolling (+ right, - left).
* `mouseReport.buttons` - this is a uint8_t in which the last 5 bits are used. These bits represent the mouse button state - bit 3 is mouse button 5, and bit 7 is mouse button 1.
When the mouse report is sent, the x, y, v, and h values are set to 0 (this is done in "pointing_device_send()", which can be overridden to avoid this behavior). This way, button states persist, but movement will only occur once. For further customization, both `pointing_device_init` and `pointing_device_task` can be overridden.
In the following example, a custom key is used to click the mouse and scroll 127 units vertically and horizontally, then undo all of that when released - because that's a totally useful function. Listen, this is an example:
```
case MS_SPECIAL:
report_mouse_t currentReport = pointing_device_get_report();
if (record->event.pressed)
{
currentReport.v = 127;
currentReport.h = 127;
currentReport.buttons |= MOUSE_BTN1; //this is defined in report.h
}
else
{
currentReport.v = -127;
currentReport.h = -127;
currentReport.buttons &= ~MOUSE_BTN1;
}
pointing_device_set_report(currentReport);
break;
```
Recall that the mouse report is set to zero (except the buttons) whenever it is sent, so the scrolling would only occur once in each case.