Window icons (#497)

src/platform/windows/icon.rs

@@ -0,0 +1,112 @@
+use std::{self, mem, ptr};
+use std::os::windows::ffi::OsStrExt;
+use std::path::Path;
+
+use winapi::ctypes::{c_int, wchar_t};
+use winapi::shared::minwindef::{BYTE, LPARAM, WPARAM};
+use winapi::shared::windef::{HICON, HWND};
+use winapi::um::winuser;
+
+use {Pixel, PIXEL_SIZE, Icon};
+use platform::platform::util;
+
+impl Pixel {
+    fn to_bgra(&mut self) {
+        mem::swap(&mut self.r, &mut self.b);
+    }
+}
+
+#[derive(Debug)]
+pub enum IconType {
+    Small = winuser::ICON_SMALL as isize,
+    Big = winuser::ICON_BIG as isize,
+}
+
+#[derive(Debug)]
+pub struct WinIcon {
+    pub handle: HICON,
+}
+
+impl WinIcon {
+    #[allow(dead_code)]
+    pub fn from_path<P: AsRef<Path>>(path: P) -> Result<Self, util::WinError> {
+        let wide_path: Vec<u16> = path.as_ref().as_os_str().encode_wide().collect();
+        let handle = unsafe {
+            winuser::LoadImageW(
+                ptr::null_mut(),
+                wide_path.as_ptr() as *const wchar_t,
+                winuser::IMAGE_ICON,
+                0, // 0 indicates that we want to use the actual width
+                0, // and height
+                winuser::LR_LOADFROMFILE,
+            ) as HICON
+        };
+        if !handle.is_null() {
+            Ok(WinIcon { handle })
+        } else {
+            Err(util::WinError::from_last_error())
+        }
+    }
+
+    pub fn from_icon(icon: Icon) -> Result<Self, util::WinError> {
+        Self::from_rgba(icon.rgba, icon.width, icon.height)
+    }
+
+    pub fn from_rgba(mut rgba: Vec<u8>, width: u32, height: u32) -> Result<Self, util::WinError> {
+        assert_eq!(rgba.len() % PIXEL_SIZE, 0);
+        let pixel_count = rgba.len() / PIXEL_SIZE;
+        assert_eq!(pixel_count, (width * height) as usize);
+        let mut and_mask = Vec::with_capacity(pixel_count);
+        let pixels = rgba.as_mut_ptr() as *mut Pixel; // how not to write idiomatic Rust
+        for pixel_index in 0..pixel_count {
+            let pixel = unsafe { &mut *pixels.offset(pixel_index as isize) };
+            and_mask.push(pixel.a.wrapping_sub(std::u8::MAX)); // invert alpha channel
+            pixel.to_bgra();
+        }
+        assert_eq!(and_mask.len(), pixel_count);
+        let handle = unsafe {
+            winuser::CreateIcon(
+                ptr::null_mut(),
+                width as c_int,
+                height as c_int,
+                1,
+                (PIXEL_SIZE * 8) as BYTE,
+                and_mask.as_ptr() as *const BYTE,
+                rgba.as_ptr() as *const BYTE,
+            ) as HICON
+        };
+        if !handle.is_null() {
+            Ok(WinIcon { handle })
+        } else {
+            Err(util::WinError::from_last_error())
+        }
+    }
+
+    pub fn set_for_window(&self, hwnd: HWND, icon_type: IconType) {
+        unsafe {
+            winuser::SendMessageW(
+                hwnd,
+                winuser::WM_SETICON,
+                icon_type as WPARAM,
+                self.handle as LPARAM,
+            );
+        }
+    }
+}
+
+impl Drop for WinIcon {
+    fn drop(&mut self) {
+        unsafe { winuser::DestroyIcon(self.handle) };
+    }
+}
+
+pub fn unset_for_window(hwnd: HWND, icon_type: IconType) {
+    unsafe {
+        winuser::SendMessageW(
+            hwnd,
+            winuser::WM_SETICON,
+            icon_type as WPARAM,
+            0 as LPARAM,
+        );
+    }
+}