fix(linux): Fix lost context after pressing K_SHIFT

This fixes typing `n>` with sil_ipa keyboard which no longer output
the expected `ŋ` because pressing the shift key reset the context.

For modifier key presses we now exit `KMX_ProcessEvent::ProcessEvent`
early.

This change also removes a redundant line from engine.c. Clearing
the context happens in `reset_context()` again if necessary.

Fixes #5591.

common/core/desktop/src/kmx/kmx_processevent.cpp

@@ -119,7 +119,10 @@ KMX_BOOL KMX_ProcessEvent::ProcessEvent(
     break;
   case KM_KBP_VKEY_SHIFT:
     KeyShiftPress(modifiers, isKeyDown);
-    break;
+    return TRUE;
+  case KM_KBP_VKEY_CONTROL:
+  case KM_KBP_VKEY_ALT:
+    return TRUE;
   }
 
   if (!isKeyDown) {
@@ -293,7 +296,6 @@ KMX_BOOL KMX_ProcessEvent::ProcessGroup(LPGROUP gp, KMX_BOOL *pOutputKeystroke)
           m_actions.QueueAction(QIT_BACK, BK_DEADKEY);  // side effect: also removes last char from context
           pdeletecontext = m_context.Buf(1);
         }
-
       } else {   // I4024   // I4128   // I4287   // I4290
         DebugLog(" ... IsLegacy = FALSE; IsTIP = TRUE");   // I4128
         m_actions.QueueAction(QIT_INVALIDATECONTEXT, 0);
@@ -313,7 +315,7 @@ KMX_BOOL KMX_ProcessEvent::ProcessGroup(LPGROUP gp, KMX_BOOL *pOutputKeystroke)
       PostString(gp->dpNoMatch, m_keyboard.Keyboard, NULL, pOutputKeystroke);
       if(m_debug_items) {
         m_debug_items->push_nomatch_exit(m_actions.Length(), gp);
-    }
+      }
     }
     else if (m_state.charCode != 0 && m_state.charCode != 0xFFFF && gp->fUsingKeys)
     {

common/core/desktop/tests/unit/kmx/013 - deadkeys.kmn

@@ -1,14 +1,14 @@
 c Description: Tests a simple deadkey rule in Unicode
-c keys: [SHIFT K_6][K_A]
-c expected: \u00E2
-c context: 
+c keys: [SHIFT K_6][K_A][SHIFT K_6][K_SHIFT][K_A][SHIFT K_6][RALT K_B][K_A][SHIFT K_6][K_CAPS][K_A]
+c expected: pass.pass.pass.pass.
+c context:
 
 store(&VERSION) '9.0'
 
 begin unicode > use(main)
 
-group(main) using keys 
+group(main) using keys
 
 + '^' > deadkey(1)
 
-dk(1) + 'a' >  U+00E2
+dk(1) + [K_A] > 'pass.'

common/core/desktop/tests/unit/kmx/031 - caps lock.kmn

@@ -1,6 +1,6 @@
 c Description: Tests Caps Lock
-c keys: [K_1][SHIFT K_2][SHIFT K_3][K_A][SHIFT K_B]
-c expected: pass.pass.pass.pass.pass.
+c keys: [K_1][SHIFT K_2][SHIFT K_3][K_A][SHIFT K_B][K_C][K_CAPS][K_D]
+c expected: pass.pass.pass.pass.pass.pass.pass.
 c capsLock: 1
 c context:
 
@@ -24,3 +24,11 @@ group(Main) using keys
 
 + 'b' > 'pass.'
 + 'B' > 'fail.'
+
+c Caps is on. The virtual key should match.
++ [SHIFT K_C] > 'fail.'
++ [K_C] > 'pass.'
+
+c Caps was pressed and released, so Caps is now off.  The virtual key should still match.
++ [SHIFT K_D] > 'fail.'
++ [K_D] > 'pass.'

linux/ibus-keyman/src/engine.c

@@ -754,7 +754,6 @@ static gboolean process_emit_keystroke_action(IBusKeymanEngine *keyman) {
 
 static gboolean process_invalidate_context_action(IBusEngine *engine) {
   IBusKeymanEngine *keyman = (IBusKeymanEngine *)engine;
-  km_kbp_context_clear(km_kbp_state_context(keyman->state));
   reset_context(engine);
   return TRUE;
 }