Input Method Editor (IME) support for text buttons

Original patch by @random (D765) with some minor work done by @campbell
and me.

At this place, I'd like call out a number of people who were involved and
deserve a big "Thank you!":
* At the first place @randon who developed and submitted the patch
* The Blendercn community which helped a lot with testing - espacially
* @yuzukyo, @leon_cheung and @kjym3
* @campbellbarton, @mont29 and @sergey for their help and advises during
* review
* @ton who realized the importance of this early on and asked me for
* reviewing

We are still not finished, as this is only the first part of the
implementaion, but there's more to come!

7 files changed, 228 insertions, 9 deletions

diff --git a/source/blender/editors/interface/CMakeLists.txt b/source/blender/editors/interface/CMakeLists.txt
index b921d17104c..972eca747b9 100644
--- a/source/blender/editors/interface/CMakeLists.txt
+++ b/source/blender/editors/interface/CMakeLists.txt
@@ -71,6 +71,12 @@ if(WITH_PYTHON)
 	add_definitions(-DWITH_PYTHON)
 endif()
 
+if(WIN32)
+	if(WITH_INPUT_IME)
+		add_definitions(-DWITH_INPUT_IME)
+	endif()
+endif()
+
 add_definitions(${GL_DEFINITIONS})
 
 blender_add_lib(bf_editor_interface "${SRC}" "${INC}" "${INC_SYS}")
diff --git a/source/blender/editors/interface/SConscript b/source/blender/editors/interface/SConscript
index 303ab7ff286..5af8bba5a9f 100644
--- a/source/blender/editors/interface/SConscript
+++ b/source/blender/editors/interface/SConscript
@@ -48,6 +48,10 @@ incs = [
 
 defs = env['BF_GL_DEFINITIONS']
 
+if env['OURPLATFORM'] in ('win32-vc', 'win32-mingw', 'win64-vc', 'win64-mingw'):
+    if env['WITH_BF_IME']:
+        defs.append('WITH_INPUT_IME')
+
 if env['WITH_BF_INTERNATIONAL']:
     defs.append('WITH_INTERNATIONAL')
 
diff --git a/source/blender/editors/interface/interface.c b/source/blender/editors/interface/interface.c
index 92017e7a967..4cbb02c4dd5 100644
--- a/source/blender/editors/interface/interface.c
+++ b/source/blender/editors/interface/interface.c
@@ -209,6 +209,11 @@ void ui_window_to_region(const ARegion *ar, int *x, int *y)
 	*y -= ar->winrct.ymin;
 }
 
+void ui_region_to_window(const ARegion *ar, int *x, int *y)
+{
+	*x += ar->winrct.xmin;
+	*y += ar->winrct.ymin;
+}
 /* ******************* block calc ************************* */
 
 void ui_block_translate(uiBlock *block, int x, int y)
diff --git a/source/blender/editors/interface/interface_draw.c b/source/blender/editors/interface/interface_draw.c
index 4dd952f0753..bcd9b9a5547 100644
--- a/source/blender/editors/interface/interface_draw.c
+++ b/source/blender/editors/interface/interface_draw.c
@@ -395,6 +395,12 @@ void UI_draw_roundbox(float minx, float miny, float maxx, float maxy, float rad)
 	ui_draw_anti_roundbox(GL_POLYGON, minx, miny, maxx, maxy, rad, roundboxtype & UI_RB_ALPHA);
 }
 
+void UI_draw_text_underline(int pos_x, int pos_y, int len, int height)
+{
+	int ofs_y = 4 * U.pixelsize;
+	glRecti(pos_x, pos_y - ofs_y, pos_x + len, pos_y - ofs_y + (height * U.pixelsize));
+}
+
 /* ************** SPECIAL BUTTON DRAWING FUNCTIONS ************* */
 
 void ui_draw_but_IMAGE(ARegion *UNUSED(ar), uiBut *but, uiWidgetColors *UNUSED(wcol), const rcti *rect)
diff --git a/source/blender/editors/interface/interface_handlers.c b/source/blender/editors/interface/interface_handlers.c
index 3a312808cee..b39c786fba7 100644
--- a/source/blender/editors/interface/interface_handlers.c
+++ b/source/blender/editors/interface/interface_handlers.c
@@ -87,6 +87,10 @@
 #include "WM_api.h"
 #include "WM_types.h"
 
+#ifdef WITH_INPUT_IME
+#  include "wm_window.h"
+#endif
+
 /* place the mouse at the scaled down location when un-grabbing */
 #define USE_CONT_MOUSE_CORRECT
 /* support dragging toggle buttons */
@@ -2425,8 +2429,50 @@ static bool ui_textedit_copypaste(uiBut *but, uiHandleButtonData *data, const in
 	return changed;
 }
 
+#ifdef WITH_INPUT_IME
+/* enable ime, and set up uibut ime data */
+static void ui_textedit_ime_begin(wmWindow *win, uiBut *UNUSED(but))
+{
+	/* XXX Is this really needed? */
+	int x, y;
+
+	/* enable IME and position to cursor, it's a trick */
+	x = win->eventstate->x;
+	/* flip y and move down a bit, prevent the IME panel cover the edit button */
+	y = win->eventstate->y - 12;
+
+	wm_window_IME_begin(win, x, y, 0, 0, true);
+}
+
+/* disable ime, and clear uibut ime data */
+static void ui_textedit_ime_end(wmWindow *win, uiBut *UNUSED(but))
+{
+	wm_window_IME_end(win);
+}
+
+void ui_but_ime_reposition(uiBut *but, int x, int y, bool complete)
+{
+	BLI_assert(but->active);
+
+	ui_region_to_window(but->active->region, &x, &y);
+	wm_window_IME_begin(but->active->window, x, y - 4, 0, 0, complete);
+}
+
+/* should be ui_but_ime_data_get */
+wmIMEData *ui_but_get_ime_data(uiBut *but)
+{
+	if (but->active && but->active->window) {
+		return but->active->window->ime_data;
+	}
+	else {
+		return NULL;
+	}
+}
+#endif  /* WITH_INPUT_IME */
+
 static void ui_textedit_begin(bContext *C, uiBut *but, uiHandleButtonData *data)
 {
+	wmWindow *win = CTX_wm_window(C);
 	int len;
 
 	if (data->str) {
@@ -2482,12 +2528,18 @@ static void ui_textedit_begin(bContext *C, uiBut *but, uiHandleButtonData *data)
 	but->flag &= ~UI_BUT_REDALERT;
 
 	ui_but_update(but);
-	
-	WM_cursor_modal_set(CTX_wm_window(C), BC_TEXTEDITCURSOR);
+
+	WM_cursor_modal_set(win, BC_TEXTEDITCURSOR);
+
+#ifdef WITH_INPUT_IME
+	ui_textedit_ime_begin(win, but);
+#endif
 }
 
 static void ui_textedit_end(bContext *C, uiBut *but, uiHandleButtonData *data)
 {
+	wmWindow *win = CTX_wm_window(C);
+
 	if (but) {
 		if (ui_but_is_utf8(but)) {
 			int strip = BLI_utf8_invalid_strip(but->editstr, strlen(but->editstr));
@@ -2518,7 +2570,11 @@ static void ui_textedit_end(bContext *C, uiBut *but, uiHandleButtonData *data)
 		but->pos = -1;
 	}
 	
-	WM_cursor_modal_restore(CTX_wm_window(C));
+	WM_cursor_modal_restore(win);
+
+#ifdef WITH_INPUT_IME
+	ui_textedit_ime_end(win, but);
+#endif
 }
 
 static void ui_textedit_next_but(uiBlock *block, uiBut *actbut, uiHandleButtonData *data)
@@ -2583,6 +2639,14 @@ static void ui_do_but_textedit(bContext *C, uiBlock *block, uiBut *but, uiHandle
 	int retval = WM_UI_HANDLER_CONTINUE;
 	bool changed = false, inbox = false, update = false;
 
+#ifdef WITH_INPUT_IME
+	wmWindow *win = CTX_wm_window(C);
+	wmIMEData *ime_data = win->ime_data;
+	bool is_ime_composing = ime_data && ime_data->is_ime_composing;
+#else
+	bool is_ime_composing = false;
+#endif
+
 	switch (event->type) {
 		case MOUSEMOVE:
 		case MOUSEPAN:
@@ -2603,6 +2667,12 @@ static void ui_do_but_textedit(bContext *C, uiBlock *block, uiBut *but, uiHandle
 		case RIGHTMOUSE:
 		case ESCKEY:
 			if (event->val == KM_PRESS) {
+#ifdef WITH_INPUT_IME
+				/* skips button handling since it is not wanted */
+				if (is_ime_composing) {
+					break;
+				}
+#endif
 				data->cancel = true;
 				data->escapecancel = true;
 				button_activate_state(C, but, BUTTON_STATE_EXIT);
@@ -2660,7 +2730,7 @@ static void ui_do_but_textedit(bContext *C, uiBlock *block, uiBut *but, uiHandle
 		}
 	}
 
-	if (event->val == KM_PRESS) {
+	if (event->val == KM_PRESS && !is_ime_composing) {
 		switch (event->type) {
 			case VKEY:
 			case XKEY:
@@ -2776,7 +2846,15 @@ static void ui_do_but_textedit(bContext *C, uiBlock *block, uiBut *but, uiHandle
 				break;
 		}
 
-		if ((event->ascii || event->utf8_buf[0]) && (retval == WM_UI_HANDLER_CONTINUE)) {
+		if ((event->ascii || event->utf8_buf[0]) &&
+		    (retval == WM_UI_HANDLER_CONTINUE)
+#ifdef WITH_INPUT_IME
+		    &&
+		    !is_ime_composing &&
+		    !WM_event_is_ime_switch(event)
+#endif
+		    )
+		{
 			char ascii = event->ascii;
 			const char *utf8_buf = event->utf8_buf;
 
@@ -2811,6 +2889,25 @@ static void ui_do_but_textedit(bContext *C, uiBlock *block, uiBut *but, uiHandle
 			update = true;
 	}
 
+#ifdef WITH_INPUT_IME
+	if (event->type == WM_IME_COMPOSITE_START || event->type == WM_IME_COMPOSITE_EVENT) {
+		changed = true;
+
+		if (event->type == WM_IME_COMPOSITE_START && but->selend > but->selsta) {
+			ui_textedit_delete_selection(but, data);
+		}
+		if (event->type == WM_IME_COMPOSITE_EVENT && ime_data->result_len) {
+			ui_textedit_type_buf(
+			        but, data,
+			        ime_data->str_result,
+			        ime_data->result_len);
+		}
+	}
+	else if (event->type == WM_IME_COMPOSITE_END) {
+		changed = true;
+	}
+#endif
+
 	if (changed) {
 		/* only update when typing for TAB key */
 		if (update && data->interactive) {
diff --git a/source/blender/editors/interface/interface_intern.h b/source/blender/editors/interface/interface_intern.h
index 328822e47ef..2c3a239b2a2 100644
--- a/source/blender/editors/interface/interface_intern.h
+++ b/source/blender/editors/interface/interface_intern.h
@@ -433,6 +433,7 @@ extern void ui_block_to_window_rctf(const struct ARegion *ar, uiBlock *block, rc
 extern void ui_window_to_block_fl(const struct ARegion *ar, uiBlock *block, float *x, float *y);
 extern void ui_window_to_block(const struct ARegion *ar, uiBlock *block, int *x, int *y);
 extern void ui_window_to_region(const ARegion *ar, int *x, int *y);
+extern void ui_region_to_window(const struct ARegion *ar, int *x, int *y);
 
 extern double ui_but_value_get(uiBut *but);
 extern void ui_but_value_set(uiBut *but, double value);
@@ -627,6 +628,11 @@ void ui_panel_menu(struct bContext *C, ARegion *ar, Panel *pa);
 uiBut *ui_but_find_old(uiBlock *block_old, const uiBut *but_new);
 uiBut *ui_but_find_new(uiBlock *block_old, const uiBut *but_new);
 
+#ifdef WITH_INPUT_IME
+void ui_but_ime_reposition(uiBut *but, int x, int y, bool complete);
+struct wmIMEData *ui_but_get_ime_data(uiBut *but);
+#endif
+
 /* interface_widgets.c */
 void ui_draw_anti_tria(float x1, float y1, float x2, float y2, float x3, float y3);
 void ui_draw_anti_roundbox(int mode, float minx, float miny, float maxx, float maxy, float rad, bool use_alpha);
diff --git a/source/blender/editors/interface/interface_widgets.c b/source/blender/editors/interface/interface_widgets.c
index c9def075666..d6c51b6b220 100644
--- a/source/blender/editors/interface/interface_widgets.c
+++ b/source/blender/editors/interface/interface_widgets.c
@@ -59,6 +59,10 @@
 
 #include "interface_intern.h"
 
+#ifdef WITH_INPUT_IME
+#  include "WM_types.h"
+#endif
+
 /* icons are 80% of height of button (16 pixels inside 20 height) */
 #define ICON_SIZE_FROM_BUTRECT(rect) (0.8f * BLI_rcti_size_y(rect))
 
@@ -1232,6 +1236,50 @@ static void ui_text_clip_right_label(uiFontStyle *fstyle, uiBut *but, const rcti
 		BLF_disable(fstyle->uifont_id, BLF_KERNING_DEFAULT);
 }
 
+#ifdef WITH_INPUT_IME
+static void widget_draw_text_ime_underline(
+        uiFontStyle *fstyle, uiWidgetColors *wcol, uiBut *but, const rcti *rect,
+        const wmIMEData *ime_data, const char *drawstr)
+{
+	int ofs_x, width;
+	int rect_x = BLI_rcti_size_x(rect);
+	int sel_start = ime_data->sel_start, sel_end = ime_data->sel_end;
+
+	if (drawstr[0] != 0) {
+		if (but->pos >= but->ofs) {
+			ofs_x = BLF_width(fstyle->uifont_id, drawstr + but->ofs, but->pos - but->ofs);
+		}
+		else {
+			ofs_x = 0;
+		}
+
+		width = BLF_width(fstyle->uifont_id, drawstr + but->ofs,
+		                  ime_data->composite_len + but->pos - but->ofs);
+
+		glColor4ubv((unsigned char *)wcol->text);
+		UI_draw_text_underline(rect->xmin + ofs_x, rect->ymin + 6 * U.pixelsize, min_ii(width, rect_x - 2) - ofs_x, 1);
+
+		/* draw the thick line */
+		if (sel_start != -1 && sel_end != -1) {
+			sel_end -= sel_start;
+			sel_start += but->pos;
+
+			if (sel_start >= but->ofs) {
+				ofs_x = BLF_width(fstyle->uifont_id, drawstr + but->ofs, sel_start - but->ofs);
+			}
+			else {
+				ofs_x = 0;
+			}
+
+			width = BLF_width(fstyle->uifont_id, drawstr + but->ofs,
+			                  sel_end + sel_start - but->ofs);
+
+			UI_draw_text_underline(rect->xmin + ofs_x, rect->ymin + 6 * U.pixelsize, min_ii(width, rect_x - 2) - ofs_x, 2);
+		}
+	}
+}
+#endif  /* WITH_INPUT_IME */
+
 static void widget_draw_text(uiFontStyle *fstyle, uiWidgetColors *wcol, uiBut *but, rcti *rect)
 {
 	int drawstr_left_len = UI_MAX_DRAW_STR;
@@ -1239,6 +1287,10 @@ static void widget_draw_text(uiFontStyle *fstyle, uiWidgetColors *wcol, uiBut *b
 	const char *drawstr_right = NULL;
 	bool use_right_only = false;
 
+#ifdef WITH_INPUT_IME
+	const wmIMEData *ime_data;
+#endif
+
 	UI_fontstyle_set(fstyle);
 	
 	if (but->editstr || (but->drawflag & UI_BUT_TEXT_LEFT))
@@ -1266,13 +1318,30 @@ static void widget_draw_text(uiFontStyle *fstyle, uiWidgetColors *wcol, uiBut *b
 			/* max length isn't used in this case,
 			 * we rely on string being NULL terminated. */
 			drawstr_left_len = INT_MAX;
-			drawstr = but->editstr;
+
+#ifdef WITH_INPUT_IME
+			/* FIXME, IME is modifying 'const char *drawstr! */
+			ime_data = ui_but_get_ime_data(but);
+
+			if (ime_data && ime_data->composite_len) {
+				/* insert composite string into cursor pos */
+				BLI_snprintf((char *)drawstr, UI_MAX_DRAW_STR, "%s%s%s",
+				             but->editstr, ime_data->str_composite,
+				             but->editstr + but->pos);
+			}
+			else
+#endif
+			{
+				drawstr = but->editstr;
+			}
 		}
 	}
 
 
-	/* text button selection and cursor */
+	/* text button selection, cursor, composite underline */
 	if (but->editstr && but->pos != -1) {
+		int but_pos_ofs;
+		int tx, ty;
 
 		/* text button selection */
 		if ((but->selend - but->selsta) > 0) {
@@ -1298,18 +1367,44 @@ static void widget_draw_text(uiFontStyle *fstyle, uiWidgetColors *wcol, uiBut *b
 		}
 
 		/* text cursor */
+		but_pos_ofs = but->pos;
+
+#ifdef WITH_INPUT_IME
+		/* if is ime compositing, move the cursor */
+		if (ime_data && ime_data->composite_len && ime_data->cursor_pos != -1) {
+			but_pos_ofs += ime_data->cursor_pos;
+		}
+#endif
+
 		if (but->pos >= but->ofs) {
 			int t;
 			if (drawstr[0] != 0) {
-				t = BLF_width(fstyle->uifont_id, drawstr + but->ofs, but->pos - but->ofs);
+				t = BLF_width(fstyle->uifont_id, drawstr + but->ofs, but_pos_ofs - but->ofs);
 			}
 			else {
 				t = 0;
 			}
 
 			glColor3f(0.20, 0.6, 0.9);
-			glRecti(rect->xmin + t, rect->ymin + 2, rect->xmin + t + 2, rect->ymax - 2);
+
+			tx = rect->xmin + t + 2;
+			ty = rect->ymin + 2;
+
+			/* draw cursor */
+			glRecti(rect->xmin + t, ty, tx, rect->ymax - 2);
 		}
+
+#ifdef WITH_INPUT_IME
+		if (ime_data && ime_data->composite_len) {
+			/* ime cursor following */
+			if (but->pos >= but->ofs) {
+				ui_but_ime_reposition(but, tx + 5, ty + 3, false);
+			}
+
+			/* composite underline */
+			widget_draw_text_ime_underline(fstyle, wcol, but, rect, ime_data, drawstr);
+		}
+#endif
 	}
 	
 	if (fstyle->kerning == 1)