Add basic IME support to SDL2 video driver

src/console_gui.cpp

@@ -374,6 +374,11 @@ struct IConsoleWindow : Window
 		this->Scroll(-wheel);
 	}
 
+	virtual void OnFocus(Window *previously_focused_window) override
+	{
+		VideoDriver::GetInstance()->EditBoxGainedFocus();
+	}
+
 	void OnFocusLost(Window *newly_focused_window) override
 	{
 		VideoDriver::GetInstance()->EditBoxLostFocus();

src/textbuf.cpp

@@ -101,6 +101,7 @@ bool Textbuf::DeleteChar(uint16 keycode)
 	/* Move the remaining characters over the marker */
 	memmove(s, s + len, this->bytes - (s - this->buf) - len);
 	this->bytes -= len;
+	if (this->markend >= this->bytes) this->markpos = this->markend = 0;
 
 	if (backspace) this->caretpos -= len;
 
@@ -251,6 +252,7 @@ void Textbuf::DeleteText(uint16 from, uint16 to, bool update)
 	/* Strip marked characters from buffer. */
 	memmove(this->buf + from, this->buf + to, this->bytes - to);
 	this->bytes -= to - from;
+	if (this->markend >= this->bytes) this->markpos = this->markend = 0;
 	this->chars -= c;
 
 	/* Fixup caret if needed. */

src/video/sdl2_v.cpp

@@ -23,6 +23,7 @@
 #include "../core/math_func.hpp"
 #include "../fileio_func.h"
 #include "../framerate_type.h"
+#include "../window_func.h"
 #include "sdl2_v.h"
 #include <SDL.h>
 #include <mutex>
@@ -60,6 +61,8 @@ static int _num_dirty_rects;
 static int _window_size_w;
 static int _window_size_h;
 
+static std::string _editing_text;
+
 void VideoDriver_SDL::MakeDirty(int left, int top, int width, int height)
 {
 	if (_num_dirty_rects < MAX_DIRTY_RECTS) {
@@ -358,6 +361,18 @@ bool VideoDriver_SDL::ClaimMousePointer()
 	return true;
 }
 
+void VideoDriver_SDL::EditBoxGainedFocus()
+{
+	SDL_StartTextInput();
+}
+
+void VideoDriver_SDL::EditBoxLostFocus()
+{
+	SDL_StopTextInput();
+	/* Clear any marked string from the current edit box. */
+	HandleTextInput(nullptr, true);
+}
+
 struct VkMapping {
 	SDL_Keycode vk_from;
 	byte vk_count;
@@ -574,6 +589,11 @@ int VideoDriver_SDL::PollEvent()
 			break;
 
 		case SDL_TEXTINPUT: {
+			if (EditBoxInGlobalFocus()) {
+				HandleTextInput(nullptr, true);
+				HandleTextInput(ev.text.text);
+				break;
+			}
 			WChar character;
 			SDL_Keycode kc = SDL_GetKeyFromName(ev.text.text);
 			uint keycode = ConvertSdlKeycodeIntoMy(kc);
@@ -582,6 +602,18 @@ int VideoDriver_SDL::PollEvent()
 			HandleKeypress(keycode, character);
 			break;
 		}
+
+		case SDL_TEXTEDITING: {
+			if (!EditBoxInGlobalFocus()) break;
+			if (ev.edit.start == 0) {
+				_editing_text = ev.edit.text;
+			} else {
+				_editing_text += ev.edit.text;
+			}
+			HandleTextInput(_editing_text.c_str(), true, _editing_text.c_str() + _editing_text.size());
+			break;
+		}
+
 		case SDL_WINDOWEVENT: {
 			if (ev.window.event == SDL_WINDOWEVENT_EXPOSED) {
 				// Force a redraw of the entire screen.

src/video/sdl2_v.h

@@ -37,6 +37,10 @@ public:
 
 	bool ClaimMousePointer() override;
 
+	void EditBoxGainedFocus() override;
+
+	void EditBoxLostFocus() override;
+
 	const char *GetName() const override { return "sdl"; }
 private:
 	int PollEvent();

src/video/video_driver.hpp

@@ -88,6 +88,11 @@ public:
 		return true;
 	}
 
+	/**
+	 * An edit box gained the input focus
+	 */
+	virtual void EditBoxGainedFocus() {}
+
 	/**
 	 * An edit box lost the input focus. Abort character compositing if necessary.
 	 */

src/window.cpp

@@ -502,11 +502,20 @@ bool Window::SetFocusedWidget(int widget_index)
 		if (this->nested_focus->type == WWT_EDITBOX) VideoDriver::GetInstance()->EditBoxLostFocus();
 	}
 	this->nested_focus = this->GetWidget<NWidgetCore>(widget_index);
+	if (this->nested_focus->type == WWT_EDITBOX) VideoDriver::GetInstance()->EditBoxGainedFocus();
 	return true;
 }
 
 /**
- * Called when window looses focus
+ * Called when window gains focus
+ */
+void Window::OnFocus(Window *previously_focused_window)
+{
+	if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) VideoDriver::GetInstance()->EditBoxGainedFocus();
+}
+
+/**
+ * Called when window loses focus
  */
 void Window::OnFocusLost(Window *newly_focused_window)
 {

src/window_gui.h

@@ -645,7 +645,7 @@ public:
 	 * Called when window gains focus
 	 * @param previously_focused_window The window that lost the focus.
 	 */
-	virtual void OnFocus(Window *previously_focused_window) {}
+	virtual void OnFocus(Window *previously_focused_window);
 
 	virtual void OnFocusLost(Window *newly_focused_window);