InputText, Examples/SDL: Emulate \t input if back-end doesn't provide it. (#1336, #2467)

+ Fix some output filename in SDL build batch files.

docs/TODO.txt

@@ -80,6 +80,7 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - input text: force scroll to end or scroll to a given line/contents (so user can implement a log or a search feature)
  - input text: a side bar that could e.g. preview where errors are. probably left to the user to draw but we'd need to give them the info there.
  - input text: a way for the user to provide syntax coloring.
+ - input text: Shift+TAB with ImGuiInputTextFlags_AllowTabInput works inconsistently depending on whether back-end emits actual Tab Key + \t Char or not (SDL doesn't).
  - input text multi-line: don't directly call AddText() which does an unnecessary vertex reserve for character count prior to clipping. and/or more line-based clipping to AddText(). and/or reorganize TextUnformatted/RenderText for more efficiency for large text (e.g TextUnformatted could clip and log separately, etc).
  - input text multi-line: support for cut/paste without selection (cut/paste the current line)
  - input text multi-line: line numbers? status bar? (follow up on #200)

examples/example_sdl_opengl2/build_win32.bat

@@ -1,8 +1,8 @@
 @REM Build for Visual Studio compiler. Run your copy of vcvars32.bat or vcvarsall.bat to setup command-line compiler.
 set OUT_DIR=Debug
-set OUT_EXE=example_sdl_opengl2.exe
+set OUT_EXE=example_sdl_opengl2
 set INCLUDES=/I.. /I..\.. /I%SDL2_DIR%\include
 set SOURCES=main.cpp ..\imgui_impl_sdl.cpp ..\imgui_impl_opengl2.cpp ..\..\imgui*.cpp
 set LIBS=/libpath:%SDL2_DIR%\lib\x86 SDL2.lib SDL2main.lib opengl32.lib
 mkdir %OUT_DIR%
-cl /nologo /Zi /MD %INCLUDES% %SOURCES% /Fe%OUT_DIR%/%OUT_DIR%.exe /Fo%OUT_DIR%/ /link %LIBS% /subsystem:console
+cl /nologo /Zi /MD %INCLUDES% %SOURCES% /Fe%OUT_DIR%/%OUT_EXE%.exe /Fo%OUT_DIR%/ /link %LIBS% /subsystem:console

examples/example_sdl_opengl3/build_win32.bat

@@ -1,6 +1,6 @@
 @REM Build for Visual Studio compiler. Run your copy of vcvars32.bat or vcvarsall.bat to setup command-line compiler.
 set OUT_DIR=Debug
-set OUT_EXE=example_sdl_opengl3.exe
+set OUT_EXE=example_sdl_opengl3
 set INCLUDES=/I.. /I..\.. /I%SDL2_DIR%\include /I..\libs\gl3w
 set SOURCES=main.cpp ..\imgui_impl_sdl.cpp ..\imgui_impl_opengl3.cpp ..\..\imgui*.cpp ..\libs\gl3w\GL\gl3w.c
 set LIBS=/libpath:%SDL2_DIR%\lib\x86 SDL2.lib SDL2main.lib opengl32.lib

imgui_widgets.cpp

@@ -3435,12 +3435,22 @@ bool ImGui::InputTextEx(const char* label, const char* hint, char* buf, int buf_
         if (state->SelectedAllMouseLock && !io.MouseDown[0])
             state->SelectedAllMouseLock = false;
 
+        // It is ill-defined whether the back-end needs to send a \t character when pressing the TAB keys.
+        // Win32 and GLFW naturally do it but not SDL.
+        const bool ignore_char_inputs = (io.KeyCtrl && !io.KeyAlt) || (is_osx && io.KeySuper);
+        if ((flags & ImGuiInputTextFlags_AllowTabInput) && IsKeyPressedMap(ImGuiKey_Tab) && !ignore_char_inputs && !io.KeyShift && !is_readonly)
+            if (!io.InputQueueCharacters.contains('\t'))
+            {
+                unsigned int c = '\t'; // Insert TAB
+                if (InputTextFilterCharacter(&c, flags, callback, callback_user_data))
+                    state->OnKeyPressed((int)c);
+            }
+
+        // Process regular text input (before we check for Return because using some IME will effectively send a Return?)
+        // We ignore CTRL inputs, but need to allow ALT+CTRL as some keyboards (e.g. German) use AltGR (which _is_ Alt+Ctrl) to input certain characters.
         if (io.InputQueueCharacters.Size > 0)
         {
-            // Process text input (before we check for Return because using some IME will effectively send a Return?)
-            // We ignore CTRL inputs, but need to allow ALT+CTRL as some keyboards (e.g. German) use AltGR (which _is_ Alt+Ctrl) to input certain characters.
-            bool ignore_inputs = (io.KeyCtrl && !io.KeyAlt) || (is_osx && io.KeySuper);
-            if (!ignore_inputs && !is_readonly && !user_nav_input_start)
+            if (!ignore_char_inputs && !is_readonly && !user_nav_input_start)
                 for (int n = 0; n < io.InputQueueCharacters.Size; n++)
                 {
                     // Insert character if they pass filtering