1 files changed, 72 insertions, 0 deletions
diff --git a/src/libs/3rdparty/winpty/misc/ClearConsole.cc b/src/libs/3rdparty/winpty/misc/ClearConsole.cc
new file mode 100644
index 0000000000..f95f8c84ca
--- /dev/null
+++ b/src/libs/3rdparty/winpty/misc/ClearConsole.cc
@@ -0,0 +1,72 @@
+/*
+ * Demonstrates that console clearing sets each cell's character to SP, not
+ * NUL, and it sets the attribute of each cell to the current text attribute.
+ *
+ * This confirms the MSDN instruction in the "Clearing the Screen" article.
+ * https://msdn.microsoft.com/en-us/library/windows/desktop/ms682022(v=vs.85).aspx
+ * It advises using GetConsoleScreenBufferInfo to get the current text
+ * attribute, then FillConsoleOutputCharacter and FillConsoleOutputAttribute to
+ * write to the console buffer.
+ */
+
+#include <windows.h>
+
+#include <cassert>
+#include <cstdio>
+#include <cstdlib>
+
+#include "TestUtil.cc"
+
+int main(int argc, char *argv[]) {
+    if (argc == 1) {
+        startChildProcess(L"CHILD");
+        return 0;
+    }
+
+    const HANDLE conout = GetStdHandle(STD_OUTPUT_HANDLE);
+
+    SetConsoleTextAttribute(conout, 0x24);
+    system("cls");
+
+    setWindowPos(0, 0, 1, 1);
+    setBufferSize(80, 25);
+    setWindowPos(0, 0, 80, 25);
+
+    CHAR_INFO buf;
+    COORD bufSize = { 1, 1 };
+    COORD bufCoord = { 0, 0 };
+    SMALL_RECT rect = { 5, 5, 5, 5 };
+    BOOL ret;
+    DWORD actual;
+    COORD writeCoord = { 5, 5 };
+
+    // After cls, each cell's character is a space, and its attributes are the
+    // default text attributes.
+    ret = ReadConsoleOutputW(conout, &buf, bufSize, bufCoord, &rect);
+    assert(ret && buf.Char.UnicodeChar == L' ' && buf.Attributes == 0x24);
+
+    // Nevertheless, it is possible to change a cell to NUL.
+    ret = FillConsoleOutputCharacterW(conout, L'\0', 1, writeCoord, &actual);
+    assert(ret && actual == 1);
+    ret = ReadConsoleOutputW(conout, &buf, bufSize, bufCoord, &rect);
+    assert(ret && buf.Char.UnicodeChar == L'\0' && buf.Attributes == 0x24);
+
+    // As well as a 0 attribute.  (As one would expect, the cell is
+    // black-on-black.)
+    ret = FillConsoleOutputAttribute(conout, 0, 1, writeCoord, &actual);
+    assert(ret && actual == 1);
+    ret = ReadConsoleOutputW(conout, &buf, bufSize, bufCoord, &rect);
+    assert(ret && buf.Char.UnicodeChar == L'\0' && buf.Attributes == 0);
+    ret = FillConsoleOutputCharacterW(conout, L'X', 1, writeCoord, &actual);
+    assert(ret && actual == 1);
+    ret = ReadConsoleOutputW(conout, &buf, bufSize, bufCoord, &rect);
+    assert(ret && buf.Char.UnicodeChar == L'X' && buf.Attributes == 0);
+
+    // The 'X' is invisible.
+    countDown(3);
+
+    ret = FillConsoleOutputAttribute(conout, 0x42, 1, writeCoord, &actual);
+    assert(ret && actual == 1);
+
+    countDown(5);
+}