Add Win32 procs needed to handle clipboard

tests/core/sys/windows/test_clipboard.odin

@@ -0,0 +1,52 @@
+//+build windows
+package test_core_sys_windows
+
+import "core:testing"
+import win32 "core:sys/windows"
+import "base:runtime"
+import "core:strings"
+import "core:mem"
+
+read_from_clipboard :: proc(wnd_handle: win32.HWND, allocator: runtime.Allocator) -> (result: string)
+{
+	if !win32.IsClipboardFormatAvailable(win32.CF_TEXT) do return;
+	
+		if !win32.OpenClipboard(wnd_handle) do return;
+		defer win32.CloseClipboard();
+		
+		clipboard_data := win32.GetClipboardData(win32.CF_TEXT); 
+		if clipboard_data != nil {
+			if cstr := cstring(win32.GlobalLock(win32.HGLOBAL(clipboard_data))); cstr != nil {
+				result = strings.clone_from_cstring(cstr, allocator);
+			}
+			win32.GlobalUnlock(win32.HGLOBAL(clipboard_data));
+		}
+	return;
+}
+
+write_to_clipboard :: proc(wnd_handle: win32.HWND, text: string)
+{
+	if !win32.OpenClipboard(wnd_handle) do return;
+	defer win32.CloseClipboard();
+	win32.EmptyClipboard();
+	
+	h_mem := win32.HGLOBAL(win32.GlobalAlloc(win32.GMEM_MOVEABLE, len(text) + 1));
+	if h_mem == nil do return;
+	
+	cstr_dst := cast([^]u8)win32.GlobalLock(h_mem);
+	defer win32.GlobalUnlock(h_mem);
+	if cstr_dst == nil do return;
+	
+	mem.copy(rawptr(cstr_dst), raw_data(text), len(text));
+	cstr_dst[len(text)] = 0;
+	
+	win32.SetClipboardData(win32.CF_TEXT, win32.HANDLE(h_mem)); 
+}
+
+
+@(test)
+verify_win32_clipboard :: proc(t: ^testing.T) {
+	write_to_clipboard(nil, "Hello everynyan! OH MY GAH");
+	clipboard_content := read_from_clipboard(nil, context.temp_allocator);
+	testing.expect_value(t, clipboard_content, "Hello everynyan! OH MY GAH");
+}