fixup! SDL2: preliminary handling SDL_TEXTINPUT

Make SDL2's textinput API more robust. We always send keyboard events if
textinput has not been enabled by the application. Moreover, we only
send key presses as text if the codepoint is valid and if it's not a known
non-printable. Keyboard events are omitted if key presses are sent as
text.

This has been tested with sdl_vnc.

#368

src/lib/sdl2/video/SDL_genode_fb_events.cc

@@ -82,48 +82,20 @@ extern "C" {
 #include "SDL_sysevents.h"
 #include "SDL_genode_fb_events.h"
 
-	static bool skipkey(Input::Keycode const keycode)
+	static bool skipcode(Genode::Codepoint const code)
 	{
-		using namespace Input;
+		if (!code.valid())
+			return true;
 
-		/* just filter some keys that might wreck havoc */
-		switch (keycode) {
-		case KEY_CAPSLOCK:   return true;
-		case KEY_LEFTALT:    return true;
-		case KEY_LEFTCTRL:   return true;
-		case KEY_LEFTSHIFT:  return true;
-		case KEY_RIGHTALT:   return true;
-		case KEY_RIGHTCTRL:  return true;
-		case KEY_RIGHTSHIFT: return true;
-		default: return false;
-		}
-	}
+		/* non-printable ascii */
+		if (code.value <= 31 || code.value == 127)
+			return true;
 
-	/* "borrowed" from SDL_windowsevents.c */
-	static int ConvertUTF32toUTF8(unsigned int codepoint, char *text)
-	{
-		if (codepoint <= 0x7F) {
-			text[0] = (char) codepoint;
-			text[1] = '\0';
-		} else if (codepoint <= 0x7FF) {
-			text[0] = 0xC0 | (char) ((codepoint >> 6) & 0x1F);
-			text[1] = 0x80 | (char) (codepoint & 0x3F);
-			text[2] = '\0';
-		} else if (codepoint <= 0xFFFF) {
-			text[0] = 0xE0 | (char) ((codepoint >> 12) & 0x0F);
-			text[1] = 0x80 | (char) ((codepoint >> 6) & 0x3F);
-			text[2] = 0x80 | (char) (codepoint & 0x3F);
-			text[3] = '\0';
-		} else if (codepoint <= 0x10FFFF) {
-			text[0] = 0xF0 | (char) ((codepoint >> 18) & 0x0F);
-			text[1] = 0x80 | (char) ((codepoint >> 12) & 0x3F);
-			text[2] = 0x80 | (char) ((codepoint >> 6) & 0x3F);
-			text[3] = 0x80 | (char) (codepoint & 0x3F);
-			text[4] = '\0';
-		} else {
-			return SDL_FALSE;
-		}
-		return SDL_TRUE;
+		/* function-key unicodes */
+		if (code.value >= 0xf000 && code.value <= 0xf72d)
+			return true;
+
+		return false;
 	}
 
 	static Genode::Constructible<Input::Session_client> input;
@@ -196,15 +168,12 @@ extern "C" {
 			curr.handle_press([&] (Input::Keycode key, Genode::Codepoint codepoint) {
 				if (mouse_button(key))
 					SDL_SendMouseButton(window, mouse_id, SDL_PRESSED, buttonmap[key]);
-				else
+				else if (skipcode(codepoint) || !SDL_IsTextInputActive())
 					SDL_SendKeyboardKey(SDL_PRESSED, getscancode(key));
-
-				if (SDL_EventState(SDL_TEXTINPUT, SDL_QUERY) && !skipkey(key)) {
-					char text[SDL_TEXTINPUTEVENT_TEXT_SIZE];
-					SDL_zeroa(text);
-					if (ConvertUTF32toUTF8(codepoint.value, text)) {
-						SDL_SendKeyboardText(text);
-					}
+				else {
+					Genode::String<5> text(codepoint);
+					if (text.valid())
+						SDL_SendKeyboardText(text.string());
 				}
 			});