ADNS-5050 / Ploopy Nano / Ploopy Mini Trackballs (#11994)

* added adns5050 sensor code, as well as implementations for the Ploopy Mini and the Ploopy Nano

* fixed spurious scrolling issue

* recommended fixes for pr linting and cleanup

keyboards/ploopyco/trackball_mini/keymaps/drag_scroll/keymap.c

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+/* Copyright 2020 Christopher Courtney, aka Drashna Jael're  (@drashna) <drashna@live.com>
+ * Copyright 2019 Sunjun Kim
+ * Copyright 2020 Ploopy Corporation
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include QMK_KEYBOARD_H
+
+// used for tracking the state
+bool is_drag_scroll = false;
+
+enum custom_keycodes {
+    DRAG_SCROLL = PLOOPY_SAFE_RANGE,
+};
+
+bool process_record_user(uint16_t keycode, keyrecord_t *record) {
+    switch (keycode) {
+        case DRAG_SCROLL:
+            if (record->event.pressed) {
+                // this toggles the state each time you tap it
+                is_drag_scroll ^= 1;
+            }
+            break;
+    }
+    return true;
+}
+
+// The real magic is here.
+// This function is called to translate the processed sensor movement
+// from the mouse sensor and translates it into x and y movement for
+// the mouse report. Normally.  So if "drag scroll" is toggled on,
+// moving the ball scrolls instead.  You could remove the  x or y here
+//  to only scroll in one direction, if you wanted, as well. In fact,
+// there is no reason that you need to send this to the mouse report.
+// You could have it register a key, instead.
+void process_mouse_user(report_mouse_t* mouse_report, int16_t x, int16_t y) {
+    if (is_drag_scroll) {
+        mouse_report->h = x;
+        mouse_report->v = y;
+    } else {
+        mouse_report->x = x;
+        mouse_report->y = y;
+    }
+}
+
+const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+    [0] = LAYOUT( /* Base */
+        KC_BTN1, KC_BTN3, KC_BTN2,
+          KC_BTN4, LT(1, KC_BTN5)
+    ),
+    [1] = LAYOUT(
+        DRAG_SCROLL, _______, _______,
+          _______, _______
+    )
+};

keyboards/ploopyco/trackball_mini/keymaps/drag_scroll/readme.md

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+# The Drag Scroll keymap for the Ploopy Trackball Mini
+
+This is a sample keymap showing off what you can do with the custom callback drivers.
+
+This particular example enables "drag scrolling". The movement of the ball is used to scroll up and down.