set taskbar button tool tips based on app language

backend/windows/taskbar_buttons.c

@@ -23,6 +23,22 @@ static HICON g_nextIcon;
 static HICON g_playIcon;
 static HICON g_pauseIcon;
 
+static wchar_t g_tooltipPlay[64] = {0};
+static wchar_t g_tooltipPause[64] = {0};
+static wchar_t g_tooltipPrev[64] = {0};
+static wchar_t g_tooltipNext[64] = {0};
+
+static void utf8_to_utf16(const char* utf8, wchar_t* utf16buf, size_t maxChars) {
+    MultiByteToWideChar(CP_UTF8, 0, utf8, -1, utf16buf, (int)maxChars);
+}
+
+void set_tooltips_utf8(const char* prev, const char* next, const char* play, const char* pause) {
+    utf8_to_utf16(play,   g_tooltipPlay,  _countof(g_tooltipPlay));
+    utf8_to_utf16(pause,  g_tooltipPause, _countof(g_tooltipPause));
+    utf8_to_utf16(prev,   g_tooltipPrev,  _countof(g_tooltipPrev));
+    utf8_to_utf16(next,   g_tooltipNext,  _countof(g_tooltipNext));
+}
+
 static HICON create_icon_from_bgra(const void *bgra, int width, int height) {
     HICON hIcon = NULL;
 
@@ -86,7 +102,7 @@ LRESULT CALLBACK OverrideWndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lPar
         if (g_taskbar && g_mainHWnd && g_playIcon && g_pauseIcon) {
             int playing = LOWORD(wParam) ? 1 : 0;
             g_thumbButtons[1].hIcon = playing ? g_pauseIcon : g_playIcon;
-            wcscpy_s(g_thumbButtons[1].szTip, ARRAYSIZE(g_thumbButtons[0].szTip), playing ? L"Pause" : L"Play");
+            wcscpy_s(g_thumbButtons[1].szTip, ARRAYSIZE(g_thumbButtons[1].szTip), playing ? g_tooltipPause : g_tooltipPlay);
             g_taskbar->lpVtbl->ThumbBarUpdateButtons(
                 g_taskbar,
                 g_mainHWnd,
@@ -129,7 +145,7 @@ int initialize_taskbar_buttons(void *hwndPtr, ThumbnailCallback cb) {
     g_thumbButtons[0].dwMask = THB_FLAGS | THB_TOOLTIP;
     g_thumbButtons[0].iId = 1;
     g_thumbButtons[0].dwFlags = THBF_ENABLED;
-    wcscpy_s(g_thumbButtons[0].szTip, ARRAYSIZE(g_thumbButtons[0].szTip), L"Previous");
+    wcscpy_s(g_thumbButtons[0].szTip, ARRAYSIZE(g_thumbButtons[0].szTip), g_tooltipPrev);
     if (g_prevIcon) {
         g_thumbButtons[0].dwMask |= THB_ICON;
         g_thumbButtons[0].hIcon = g_prevIcon;
@@ -138,7 +154,7 @@ int initialize_taskbar_buttons(void *hwndPtr, ThumbnailCallback cb) {
     g_thumbButtons[1].dwMask = THB_FLAGS | THB_TOOLTIP;
     g_thumbButtons[1].iId = 2;
     g_thumbButtons[1].dwFlags = THBF_ENABLED;
-    wcscpy_s(g_thumbButtons[1].szTip, ARRAYSIZE(g_thumbButtons[1].szTip), L"Play");
+    wcscpy_s(g_thumbButtons[1].szTip, ARRAYSIZE(g_thumbButtons[1].szTip), g_tooltipPlay);
     if (g_playIcon) {
         g_thumbButtons[1].dwMask |= THB_ICON;
         g_thumbButtons[1].hIcon = g_playIcon;
@@ -147,7 +163,7 @@ int initialize_taskbar_buttons(void *hwndPtr, ThumbnailCallback cb) {
     g_thumbButtons[2].dwMask = THB_FLAGS | THB_TOOLTIP;
     g_thumbButtons[2].iId = 3;
     g_thumbButtons[2].dwFlags = THBF_ENABLED;
-    wcscpy_s(g_thumbButtons[2].szTip, ARRAYSIZE(g_thumbButtons[2].szTip), L"Next");
+    wcscpy_s(g_thumbButtons[2].szTip, ARRAYSIZE(g_thumbButtons[2].szTip), g_tooltipNext);
     if (g_nextIcon) {
         g_thumbButtons[2].dwMask |= THB_ICON;
         g_thumbButtons[2].hIcon = g_nextIcon;

backend/windows/taskbar_buttons.go

@@ -4,6 +4,7 @@ package windows
 
 /*
 #cgo LDFLAGS: -lole32
+#include <stdlib.h>
 #include "taskbar_buttons.h"
 
 extern void goButtonClicked(int);
@@ -31,6 +32,22 @@ func InitializeTaskbarIcons(prev, next, play, pause image.Image) error {
 	return nil
 }
 
+// SetTaskbarButtonToolTips should be called before InitializeTaskbarButtons to
+// set the tool tips that will be used for the buttons
+func SetTaskbarButtonToolTips(prev, next, play, pause string) error {
+	cPlay := C.CString(play)
+	defer C.free(unsafe.Pointer(cPlay))
+	cPause := C.CString(pause)
+	defer C.free(unsafe.Pointer(cPause))
+	cPrev := C.CString(prev)
+	defer C.free(unsafe.Pointer(cPrev))
+	cNext := C.CString(next)
+	defer C.free(unsafe.Pointer(cNext))
+	C.set_tooltips_utf8(cPrev, cNext, cPlay, cPause)
+
+	return nil
+}
+
 func InitializeTaskbarButtons(hwnd uintptr, callback func(TaskbarButton)) error {
 	gTaskbarButtonCallback = callback
 	C.initialize_taskbar_buttons(unsafe.Pointer(hwnd), C.ThumbnailCallback(C.goButtonClicked))

backend/windows/taskbar_buttons.h

@@ -6,6 +6,10 @@ extern "C" {
 
 typedef void (*ThumbnailCallback)(int buttonId);
 
+// sets the tool tip strings for prev, next, play, and pause
+// should be called before initialize_taskbar_buttons or they will not have tool tips
+void set_tooltips_utf8(const char* prev, const char* next, const char* play, const char* pause);
+
 // sets the icons that will be used for the buttons.
 // the arguments are pointers to BGRA pixel data, and the dimensions (w, h) of all 4 images.
 int initialize_taskbar_icons(const void *bgraPrev, const void *bgraNext, const void *bgraPlay, const void *bgraPause, int width, int height);

backend/windows/taskbar_buttons_unsupported.go

@@ -13,6 +13,10 @@ func InitializeTaskbarButtons(hwnd uintptr, callback func(TaskbarButton)) error
 	return err
 }
 
+func SetTaskbarButtonToolTips(prev, next, play, pause string) error {
+	return err
+}
+
 func InitializeTaskbarIcons(prev, next, play, pause image.Image) error {
 	return err
 }