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- # Modifier Keys :id=modifier-keys
-
- These allow you to combine a modifier with a keycode. When pressed, the keydown event for the modifier, then `kc` will be sent. On release, the keyup event for `kc`, then the modifier will be sent.
-
- |Key |Aliases |Description |
- |----------|----------------------------------|------------------------------------------------------|
- |`LCTL(kc)`|`C(kc)` |Hold Left Control and press `kc` |
- |`LSFT(kc)`|`S(kc)` |Hold Left Shift and press `kc` |
- |`LALT(kc)`|`A(kc)`, `LOPT(kc)` |Hold Left Alt and press `kc` |
- |`LGUI(kc)`|`G(kc)`, `LCMD(kc)`, `LWIN(kc)` |Hold Left GUI and press `kc` |
- |`RCTL(kc)`| |Hold Right Control and press `kc` |
- |`RSFT(kc)`| |Hold Right Shift and press `kc` |
- |`RALT(kc)`|`ROPT(kc)`, `ALGR(kc)` |Hold Right Alt and press `kc` |
- |`RGUI(kc)`|`RCMD(kc)`, `LWIN(kc)` |Hold Right GUI and press `kc` |
- |`LSG(kc)` |`SGUI(kc)`, `SCMD(kc)`, `SWIN(kc)`|Hold Left Shift and GUI and press `kc` |
- |`LAG(kc)` | |Hold Left Alt and Left GUI and press `kc` |
- |`RSG(kc)` | |Hold Right Shift and Right GUI and press `kc` |
- |`RAG(kc)` | |Hold Right Alt and Right GUI and press `kc` |
- |`LCA(kc)` | |Hold Left Control and Alt and press `kc` |
- |`LSA(kc)` | |Hold Left Shift and Left Alt and press `kc` |
- |`RSA(kc)` |`SAGR(kc)` |Hold Right Shift and Right Alt (AltGr) and press `kc` |
- |`RCS(kc)` | |Hold Right Control and Right Shift and press `kc` |
- |`LCAG(kc)`| |Hold Left Control, Alt and GUI and press `kc` |
- |`MEH(kc)` | |Hold Left Control, Shift and Alt and press `kc` |
- |`HYPR(kc)`| |Hold Left Control, Shift, Alt and GUI and press `kc` |
-
- You can also chain them, for example `LCTL(LALT(KC_DEL))` or `C(A(KC_DEL))` makes a key that sends Control+Alt+Delete with a single keypress.
-
- # Checking Modifier State :id=checking-modifier-state
-
- The current modifier state can mainly be accessed with two functions: `get_mods()` for normal modifiers and modtaps and `get_oneshot_mods()` for one-shot modifiers (unless they're held, in which case they act like normal modifier keys).
-
- The presence of one or more specific modifiers in the current modifier state can be detected by ANDing the modifier state with a mod mask corresponding to the set of modifiers you want to match for. The reason why bitwise operators are used is that the modifier state is stored as a single byte in the format (GASC)<sub>R</sub>(GASC)<sub>L</sub>.
-
- Thus, to give an example, `01000010` would be the internal representation of LShift+RAlt.
- For more information on bitwise operators in C, click [here](https://en.wikipedia.org/wiki/Bitwise_operations_in_C) to open the Wikipedia page on the topic.
-
- In practice, this means that you can check whether a given modifier is active with `get_mods() & MOD_BIT(KC_<modifier>)` (see the [list of modifier keycodes](keycodes_basic.md#modifiers)) or with `get_mods() & MOD_MASK_<modifier>` if the difference between left and right hand modifiers is not important and you want to match both. Same thing can be done for one-shot modifiers if you replace `get_mods()` with `get_oneshot_mods()`.
-
- To check that *only* a specific set of mods is active at a time, AND the modifier state and your desired mod mask as explained above and compare the result to the mod mask itself: `get_mods() & <mod mask> == <mod mask>`.
-
- For example, let's say you want to trigger a piece of custom code if one-shot left control and one-shot left shift are on but every other one-shot mods are off. To do so, you can compose the desired mod mask by combining the mod bits for left control and shift with `(MOD_BIT(KC_LCTL) | MOD_BIT(KC_LSFT))` and then plug it in: `get_oneshot_mods() & (MOD_BIT(KC_LCTL) | MOD_BIT(KC_LSFT)) == (MOD_BIT(KC_LCTL) | MOD_BIT(KC_LSFT))`. Using `MOD_MASK_CS` instead for the mod bitmask would have forced you to press four modifier keys (both versions of control and shift) to fulfill the condition.
-
- The full list of mod masks is as follows:
-
- | Mod Mask Name | Matching Modifiers |
- |--------------------|------------------------------------------------|
- | `MOD_MASK_CTRL` | LCTRL , RCTRL |
- | `MOD_MASK_SHIFT` | LSHIFT , RSHIFT |
- | `MOD_MASK_ALT` | LALT , RALT |
- | `MOD_MASK_GUI` | LGUI , RGUI |
- | `MOD_MASK_CS` | CTRL , SHIFT |
- | `MOD_MASK_CA` | (L/R)CTRL , (L/R)ALT |
- | `MOD_MASK_CG` | (L/R)CTRL , (L/R)GUI |
- | `MOD_MASK_SA` | (L/R)SHIFT , (L/R)ALT |
- | `MOD_MASK_SG` | (L/R)SHIFT , (L/R)GUI |
- | `MOD_MASK_AG` | (L/R)ALT , (L/R)GUI |
- | `MOD_MASK_CSA` | (L/R)CTRL , (L/R)SHIFT , (L/R)ALT |
- | `MOD_MASK_CSG` | (L/R)CTRL , (L/R)SHIFT , (L/R)GUI |
- | `MOD_MASK_CAG` | (L/R)CTRL , (L/R)ALT , (L/R)GUI |
- | `MOD_MASK_SAG` | (L/R)SHIFT , (L/R)ALT , (L/R)GUI |
- | `MOD_MASK_CSAG` | (L/R)CTRL , (L/R)SHIFT , (L/R)ALT , (L/R)GUI |
-
- Aside from accessing the currently active modifiers using `get_mods()`, there exists some other functions you can use to modify the modifier state, where the `mods` argument refers to the modifiers bitmask.
-
- * `add_mods(mods)`: Enable `mods` without affecting any other modifiers
- * `register_mods(mods)`: Like `add_mods` but send a keyboard report immediately.
- * `del_mods(mods)`: Disable `mods` without affecting any other modifiers
- * `unregister_mods(mods)`: Like `del_mods` but send a keyboard report immediately.
- * `set_mods(mods)`: Overwrite current modifier state with `mods`
- * `clear_mods()`: Reset the modifier state by disabling all modifiers
-
- Similarly, in addition to `get_oneshot_mods()`, there also exists these functions for one-shot mods:
-
- * `add_oneshot_mods(mods)`: Enable `mods` without affecting any other one-shot modifiers
- * `del_oneshot_mods(mods)`: Disable `mods` without affecting any other one-shot modifiers
- * `set_oneshot_mods(mods)`: Overwrite current one-shot modifier state with `mods`
- * `clear_oneshot_mods()`: Reset the one-shot modifier state by disabling all one-shot modifiers
-
- ## Examples :id=examples
-
- The following examples use [advanced macro functions](feature_macros.md#advanced-macro-functions) which you can read more about in the [documentation page on macros](feature_macros.md).
-
- ### Alt + Escape for Alt + Tab :id=alt-escape-for-alt-tab
-
- Simple example where chording Left Alt with `KC_ESC` makes it behave like `KC_TAB` for alt-tabbing between applications. This example strictly checks if only Left Alt is active, meaning you can't do Alt+Shift+Esc to switch between applications in reverse order. Also keep in mind that this removes the ability to trigger the actual Alt+Escape keyboard shortcut, though it keeps the ability to do AltGr+Escape.
-
- ```c
- bool process_record_user(uint16_t keycode, keyrecord_t *record) {
- switch (keycode) {
-
- case KC_ESC:
- // Detect the activation of only Left Alt
- if ((get_mods() & MOD_BIT(KC_LALT)) == MOD_BIT(KC_LALT)) {
- if (record->event.pressed) {
- // No need to register KC_LALT because it's already active.
- // The Alt modifier will apply on this KC_TAB.
- register_code(KC_TAB);
- } else {
- unregister_code(KC_TAB);
- }
- // Do not let QMK process the keycode further
- return false;
- }
- // Else, let QMK process the KC_ESC keycode as usual
- return true;
-
- }
- return true;
- };
- ```
-
- ### Shift + Backspace for Delete :id=shift-backspace-for-delete
-
- Advanced example where the original behaviour of shift is cancelled when chorded with `KC_BSPC` and is instead fully replaced by `KC_DEL`. Two main variables are created to make this work well: `mod_state` and `delkey_registered`. The first one stores the modifier state and is used to restore it after registering `KC_DEL`. The second variable is a boolean variable (true or false) which keeps track of the status of `KC_DEL` to manage the release of the whole Backspace/Delete key correctly.
-
- As opposed to the previous example, this doesn't use strict modifier checking. Pressing `KC_BSPC` while one or two shifts are active is enough to trigger this custom code, regardless of the state of other modifiers. That approach offers some perks: Ctrl+Shift+Backspace lets us delete the next word (Ctrl+Delete) and Ctrl+Alt+Shift+Backspace lets us execute the Ctrl+Alt+Del keyboard shortcut.
-
- ```c
- // Initialize variable holding the binary
- // representation of active modifiers.
- uint8_t mod_state;
- bool process_record_user(uint16_t keycode, keyrecord_t *record) {
- // Store the current modifier state in the variable for later reference
- mod_state = get_mods();
- switch (keycode) {
-
- case KC_BSPC:
- {
- // Initialize a boolean variable that keeps track
- // of the delete key status: registered or not?
- static bool delkey_registered;
- if (record->event.pressed) {
- // Detect the activation of either shift keys
- if (mod_state & MOD_MASK_SHIFT) {
- // First temporarily canceling both shifts so that
- // shift isn't applied to the KC_DEL keycode
- del_mods(MOD_MASK_SHIFT);
- register_code(KC_DEL);
- // Update the boolean variable to reflect the status of KC_DEL
- delkey_registered = true;
- // Reapplying modifier state so that the held shift key(s)
- // still work even after having tapped the Backspace/Delete key.
- set_mods(mod_state);
- return false;
- }
- } else { // on release of KC_BSPC
- // In case KC_DEL is still being sent even after the release of KC_BSPC
- if (delkey_registered) {
- unregister_code(KC_DEL);
- delkey_registered = false;
- return false;
- }
- }
- // Let QMK process the KC_BSPC keycode as usual outside of shift
- return true;
- }
-
- }
- return true;
- };
- ```
-
- # Legacy Content :id=legacy-content
-
- This page used to encompass a large set of features. We have moved many sections that used to be part of this page to their own pages. Everything below this point is simply a redirect so that people following old links on the web find what they're looking for.
-
- ## Layers :id=switching-and-toggling-layers
-
- * [Layers](feature_layers.md)
-
- ## Mod-Tap :id=mod-tap
-
- * [Mod-Tap](mod_tap.md)
-
- ## One Shot Keys :id=one-shot-keys
-
- * [One Shot Keys](one_shot_keys.md)
-
- ## Tap-Hold Configuration Options :id=tap-hold-configuration-options
-
- * [Tap-Hold Configuration Options](tap_hold.md)
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