From 7e5951162fea26064d48826be8109bdf358f4a8d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?L=C3=A1szl=C3=B3=20Monda?= <laci@monda.hu>
Date: Sun, 9 Jul 2017 02:09:22 +0200
Subject: [PATCH] Make Alt+Tab keymapping and the like work as assumed.

---
 right/src/usb_report_updater.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/right/src/usb_report_updater.c b/right/src/usb_report_updater.c
index 8a7bb06..f684252 100644
--- a/right/src/usb_report_updater.c
+++ b/right/src/usb_report_updater.c
@@ -130,6 +130,8 @@ void UpdateActiveUsbReports()
     uint8_t basicScancodeIndex = 0;
     uint8_t mediaScancodeIndex = 0;
     uint8_t systemScancodeIndex = 0;
+    static uint8_t previousLayer = LAYER_ID_BASE;
+    static uint8_t previousModifiers = 0;
     uint8_t activeLayer = getActiveLayer();
 
     for (uint8_t slotId=0; slotId<SLOT_COUNT; slotId++) {
@@ -174,4 +176,14 @@ void UpdateActiveUsbReports()
             }
         }
     }
+
+    // When a layer switcher key gets pressed along with another key that produces some modifiers
+    // and the accomanying key gets released then keep the related modifiers active a long as the
+    // layer switcher key stays pressed.  Useful for Alt+Tab keymappings and the like.
+    if (activeLayer != LAYER_ID_BASE && activeLayer == previousLayer && basicScancodeIndex == 0) {
+        ActiveUsbBasicKeyboardReport->modifiers |= previousModifiers;
+    }
+
+    previousLayer = activeLayer;
+    previousModifiers = ActiveUsbBasicKeyboardReport->modifiers;
 }