2 files changed, 74 insertions, 0 deletions

diff --git a/textscreen/txt_main.h b/textscreen/txt_main.h
index 601548e5..a415ee1b 100644
--- a/textscreen/txt_main.h
+++ b/textscreen/txt_main.h
@@ -69,6 +69,16 @@ typedef enum
     TXT_COLOR_BRIGHT_WHITE,
 } txt_color_t;
 
+// Modifier keys.
+
+typedef enum
+{
+    TXT_MOD_SHIFT,
+    TXT_MOD_CTRL,
+    TXT_MOD_ALT,
+    TXT_NUM_MODIFIERS
+} txt_modifier_t;
+
 // Initialize the screen
 // Returns 1 if successful, 0 if failed.
 
@@ -94,6 +104,10 @@ void TXT_UpdateScreen(void);
 
 int TXT_GetChar(void);
 
+// Read the current state of modifier keys that are held down.
+
+int TXT_GetModifierState(txt_modifier_t mod);
+
 // Provides a short description of a key code, placing into the 
 // provided buffer.
 
diff --git a/textscreen/txt_sdl.c b/textscreen/txt_sdl.c
index 5ae151e9..767c9b3e 100644
--- a/textscreen/txt_sdl.c
+++ b/textscreen/txt_sdl.c
@@ -63,6 +63,8 @@ static int key_mapping = 1;
 static TxtSDLEventCallbackFunc event_callback;
 static void *event_callback_data;
 
+static int modifier_state[TXT_NUM_MODIFIERS];
+
 // Font we are using:
 
 static txt_font_t *font;
@@ -493,6 +495,48 @@ static int MouseHasMoved(void)
     }
 }
 
+// Examine a key press/release and update the modifier key state
+// if necessary.
+
+static void UpdateModifierState(SDL_keysym *sym, int pressed)
+{
+    txt_modifier_t mod;
+
+    switch (sym->sym)
+    {
+        case SDLK_LSHIFT:
+        case SDLK_RSHIFT:
+            mod = TXT_MOD_SHIFT;
+            break;
+
+        case SDLK_LCTRL:
+        case SDLK_RCTRL:
+            mod = TXT_MOD_CTRL;
+            break;
+
+        case SDLK_LALT:
+        case SDLK_RALT:
+#if !SDL_VERSION_ATLEAST(1, 3, 0)
+        case SDLK_LMETA:
+        case SDLK_RMETA:
+#endif
+            mod = TXT_MOD_ALT;
+            break;
+
+        default:
+            return;
+    }
+
+    if (pressed)
+    {
+        ++modifier_state[mod];
+    }
+    else
+    {
+        --modifier_state[mod];
+    }
+}
+
 signed int TXT_GetChar(void)
 {
     SDL_Event ev;
@@ -522,8 +566,14 @@ signed int TXT_GetChar(void)
                 break;
 
             case SDL_KEYDOWN:
+                UpdateModifierState(&ev.key.keysym, 1);
+
                 return TranslateKey(&ev.key.keysym);
 
+            case SDL_KEYUP:
+                UpdateModifierState(&ev.key.keysym, 0);
+                break;
+
             case SDL_QUIT:
                 // Quit = escape
                 return 27;
@@ -542,6 +592,16 @@ signed int TXT_GetChar(void)
     return -1;
 }
 
+int TXT_GetModifierState(txt_modifier_t mod)
+{
+    if (mod < TXT_NUM_MODIFIERS)
+    {
+        return modifier_state[mod] > 0;
+    }
+
+    return 0;
+}
+
 static const char *SpecialKeyName(int key)
 {
     switch (key)