add beginnings of painting

window/src/os/windows/gdi.rs

@@ -0,0 +1,106 @@
+use crate::bitmaps::BitmapImage;
+use failure::Fallible;
+use std::io::Error as IoError;
+use winapi::shared::windef::*;
+use winapi::um::wingdi::*;
+
+pub struct GdiBitmap {
+    hdc: HDC,
+    hbitmap: HBITMAP,
+    data: *mut u8,
+    width: usize,
+    height: usize,
+}
+
+impl BitmapImage for GdiBitmap {
+    unsafe fn pixel_data(&self) -> *const u8 {
+        self.data
+    }
+
+    unsafe fn pixel_data_mut(&mut self) -> *mut u8 {
+        self.data
+    }
+
+    fn image_dimensions(&self) -> (usize, usize) {
+        (self.width, self.height)
+    }
+}
+
+impl Drop for GdiBitmap {
+    fn drop(&mut self) {
+        unsafe {
+            DeleteObject(self.hbitmap as _);
+        }
+        unsafe {
+            DeleteObject(self.hdc as _);
+        }
+    }
+}
+
+impl GdiBitmap {
+    pub fn hdc(&self) -> HDC {
+        self.hdc
+    }
+
+    pub fn hbitmap(&self) -> HBITMAP {
+        self.hbitmap
+    }
+
+    pub fn new_compatible(width: usize, height: usize, hdc: HDC) -> Fallible<Self> {
+        let hdc = unsafe { CreateCompatibleDC(hdc) };
+        if hdc.is_null() {
+            let err = IoError::last_os_error();
+            failure::bail!("CreateCompatibleDC: {}", err);
+        }
+
+        let mut data = std::ptr::null_mut();
+        let bmi = BITMAPINFO {
+            bmiHeader: BITMAPINFOHEADER {
+                biSize: std::mem::size_of::<BITMAPINFOHEADER>() as u32,
+                biPlanes: 1,
+                biBitCount: 32,
+                biWidth: width as i32,
+                biHeight: height as i32,
+                biClrImportant: 0,
+                biClrUsed: 0,
+                biCompression: 0,
+                biSizeImage: width as u32 * height as u32 * 4,
+                biXPelsPerMeter: 0,
+                biYPelsPerMeter: 0,
+            },
+            bmiColors: [RGBQUAD {
+                rgbBlue: 0,
+                rgbRed: 0,
+                rgbGreen: 0,
+                rgbReserved: 0,
+            }],
+        };
+        let hbitmap = unsafe {
+            CreateDIBSection(
+                hdc,
+                &bmi,
+                DIB_RGB_COLORS,
+                &mut data,
+                std::ptr::null_mut(),
+                0,
+            )
+        };
+
+        if hbitmap.is_null() {
+            let err = IoError::last_os_error();
+            failure::bail!("CreateDIBSection: {}", err);
+        }
+
+        unsafe {
+            SelectObject(hdc, hbitmap as _);
+        }
+
+        Ok(Self {
+            hdc,
+            hbitmap,
+            data: data as *mut u8,
+            width,
+            height,
+        })
+    }
+}

window/src/os/windows/mod.rs

@@ -1,3 +1,4 @@
+pub mod gdi;
 pub mod window;
 
 /// Convert a rust string to a windows wide string

window/src/os/windows/window.rs

@@ -1,4 +1,6 @@
+use super::gdi::*;
 use super::*;
+use crate::bitmaps::*;
 use failure::Fallible;
 use std::io::Error as IoError;
 use std::ptr::{null, null_mut};
@@ -6,6 +8,7 @@ use std::sync::{Arc, Mutex};
 use winapi::shared::minwindef::*;
 use winapi::shared::windef::*;
 use winapi::um::libloaderapi::GetModuleHandleW;
+use winapi::um::wingdi::*;
 use winapi::um::winuser::*;
 
 pub trait WindowCallbacks {
@@ -30,6 +33,14 @@ pub struct Window {
     inner: Arc<Mutex<WindowInner>>,
 }
 
+fn rect_width(r: &RECT) -> i32 {
+    r.right - r.left
+}
+
+fn rect_height(r: &RECT) -> i32 {
+    r.bottom - r.top
+}
+
 fn adjust_client_to_window_dimensions(width: usize, height: usize) -> (i32, i32) {
     let mut rect = RECT {
         left: 0,
@@ -39,9 +50,7 @@ fn adjust_client_to_window_dimensions(width: usize, height: usize) -> (i32, i32)
     };
     unsafe { AdjustWindowRect(&mut rect, WS_POPUP | WS_SYSMENU | WS_CAPTION, 0) };
 
-    let width = rect.right - rect.left;
-    let height = rect.bottom - rect.top;
-    (width, height)
+    (rect_width(&rect), rect_height(&rect))
 }
 
 fn arc_to_pointer(arc: &Arc<Mutex<WindowInner>>) -> *const Mutex<WindowInner> {
@@ -229,10 +238,47 @@ fn enable_dark_mode(hwnd: HWND) {
     }
 }
 
+unsafe fn wm_paint(hwnd: HWND, _msg: UINT, _wparam: WPARAM, _lparam: LPARAM) -> Option<LRESULT> {
+    if let Some(_inner) = arc_from_hwnd(hwnd) {
+        let dc = GetDC(hwnd);
+
+        let mut rect = RECT {
+            left: 0,
+            bottom: 0,
+            right: 0,
+            top: 0,
+        };
+        GetClientRect(hwnd, &mut rect);
+        let width = rect_width(&rect) as usize;
+        let height = rect_height(&rect) as usize;
+
+        let mut bitmap = GdiBitmap::new_compatible(width, height, dc).unwrap();
+
+        bitmap.clear(Color::rgb(0, 0, 0));
+        BitBlt(
+            dc,
+            0,
+            0,
+            width as i32,
+            height as i32,
+            bitmap.hdc(),
+            0,
+            0,
+            SRCCOPY,
+        );
+        ValidateRect(hwnd, std::ptr::null());
+
+        Some(0)
+    } else {
+        None
+    }
+}
+
 unsafe fn do_wnd_proc(hwnd: HWND, msg: UINT, wparam: WPARAM, lparam: LPARAM) -> Option<LRESULT> {
     match msg {
-        WM_NCCREATE => return wm_nccreate(hwnd, msg, wparam, lparam),
-        WM_NCDESTROY => return wm_ncdestroy(hwnd, msg, wparam, lparam),
+        WM_NCCREATE => wm_nccreate(hwnd, msg, wparam, lparam),
+        WM_NCDESTROY => wm_ncdestroy(hwnd, msg, wparam, lparam),
+        WM_PAINT => wm_paint(hwnd, msg, wparam, lparam),
         WM_CLOSE => {
             if let Some(inner) = arc_from_hwnd(hwnd) {
                 let mut inner = inner.lock().unwrap();