feat: support light/dark theme and adherence to system theme (#140)

src/painter.rs

@@ -1,4 +1,7 @@
 use crate::app::SwitchAppsState;
+use crate::utils::RegKey;
+use anyhow::Result;
+use windows::core::w;
 use windows::Win32::Foundation::{COLORREF, RECT};
 use windows::Win32::Graphics::Gdi::{
     BeginPaint, BitBlt, CreateCompatibleBitmap, CreateCompatibleDC, CreateSolidBrush, DeleteDC,
@@ -8,10 +11,14 @@ use windows::Win32::Graphics::Gdi::{
 use windows::Win32::UI::WindowsAndMessaging::{DrawIconEx, DI_NORMAL};
 use windows::Win32::{Foundation::HWND, Graphics::Gdi::GetDC};
 
-// window background color
-pub const BG_COLOR: COLORREF = COLORREF(0x3b3b3b);
-// selected icon box color
-pub const FG_COLOR: COLORREF = COLORREF(0x4c4c4c);
+// window background color in dark theme
+pub const BG_DARK_COLOR: COLORREF = COLORREF(0x3b3b3b);
+// selected icon box color in dark theme
+pub const FG_DARK_COLOR: COLORREF = COLORREF(0x4c4c4c);
+// window background color in light theme
+pub const BG_LIGHT_COLOR: COLORREF = COLORREF(0xf2f2f2);
+// selected icon box color in light theme
+pub const FG_LIGHT_COLOR: COLORREF = COLORREF(0xe0e0e0);
 // minimum icon size
 pub const ICON_SIZE: i32 = 64;
 // window padding
@@ -35,13 +42,27 @@ pub struct GdiAAPainter {
     size: i32,
     // scale
     scale: i32,
+    // color
+    fg_color: COLORREF,
+    bg_color: COLORREF,
 }
 
 impl GdiAAPainter {
     /// Creates a new [GdiAAPainter] instance.
     ///
     /// The `scale` must be a multiple of 2, for example 2, 4, 6, 8, 12 ...
     pub fn new(hwnd: HWND, scale: i32) -> Self {
+        let light_theme = match is_light_theme() {
+            Ok(v) => v,
+            Err(_) => {
+                warn!("Fail to get system theme");
+                false
+            }
+        };
+        let (fg_color, bg_color) = match light_theme {
+            true => (FG_LIGHT_COLOR, BG_LIGHT_COLOR),
+            false => (FG_DARK_COLOR, BG_DARK_COLOR),
+        };
         GdiAAPainter {
             mem_hdc: Default::default(),
             mem_map: Default::default(),
@@ -52,6 +73,8 @@ impl GdiAAPainter {
             height: 0,
             size: 0,
             scale,
+            fg_color,
+            bg_color,
         }
     }
 
@@ -86,7 +109,7 @@ impl GdiAAPainter {
             let mem_map = CreateCompatibleBitmap(hdc, width, height);
             SelectObject(mem_dc, mem_map);
 
-            let brush = CreateSolidBrush(BG_COLOR);
+            let brush = CreateSolidBrush(self.fg_color);
             let rect = RECT {
                 left: 0,
                 top: 0,
@@ -164,7 +187,7 @@ impl GdiAAPainter {
                 right: self.width * self.scale,
                 bottom: self.width * self.scale,
             };
-            FillRect(self.scaled_hdc, &rect as _, CreateSolidBrush(FG_COLOR));
+            FillRect(self.scaled_hdc, &rect as _, CreateSolidBrush(self.fg_color));
 
             let cy = (WINDOW_BORDER_SIZE + ICON_BORDER_SIZE) * self.scale;
             let brush_icon = HBRUSH::default();
@@ -183,7 +206,7 @@ impl GdiAAPainter {
                         right,
                         bottom,
                     };
-                    FillRect(self.scaled_hdc, &rect as _, CreateSolidBrush(BG_COLOR));
+                    FillRect(self.scaled_hdc, &rect as _, CreateSolidBrush(self.bg_color));
                 }
 
                 let cx = cy + item_size * (i as i32);
@@ -202,3 +225,12 @@ impl GdiAAPainter {
         }
     }
 }
+
+fn is_light_theme() -> Result<bool> {
+    let reg_key = RegKey::new_hkcu(
+        w!("Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize"),
+        w!("SystemUsesLightTheme"),
+    )?;
+    let value = reg_key.get_int()?;
+    Ok(value == 1)
+}

src/utils/regedit.rs

@@ -3,7 +3,8 @@ use windows::core::PCWSTR;
 use windows::Win32::Foundation::ERROR_FILE_NOT_FOUND;
 use windows::Win32::System::Registry::{
     RegCloseKey, RegDeleteValueW, RegGetValueW, RegOpenKeyExW, RegSetValueExW, HKEY,
-    HKEY_CURRENT_USER, KEY_ALL_ACCESS, REG_SZ, REG_VALUE_TYPE, RRF_RT_REG_SZ,
+    HKEY_CURRENT_USER, KEY_ALL_ACCESS, REG_DWORD_BIG_ENDIAN, REG_SZ, REG_VALUE_TYPE,
+    RRF_RT_REG_DWORD, RRF_RT_REG_SZ,
 };
 
 #[derive(Debug)]
@@ -57,6 +58,35 @@ impl RegKey {
         Ok(Some(buffer[..len].to_vec()))
     }
 
+    pub fn get_int(&self) -> Result<u32> {
+        let mut value: [u8; 4] = Default::default();
+        let mut size: u32 = std::mem::size_of_val(&value) as u32;
+        let mut kind: REG_VALUE_TYPE = Default::default();
+        let ret = unsafe {
+            RegGetValueW(
+                self.hkey,
+                None,
+                self.name,
+                RRF_RT_REG_DWORD,
+                Some(&mut kind),
+                Some(value.as_mut_ptr() as *mut _),
+                Some(&mut size),
+            )
+        };
+        if ret.is_err() {
+            bail!(
+                "Fail to get reg value, {:?}",
+                windows::core::Error::from(ret)
+            );
+        }
+        let value = if kind == REG_DWORD_BIG_ENDIAN {
+            u32::from_be_bytes(value)
+        } else {
+            u32::from_le_bytes(value)
+        };
+        Ok(value)
+    }
+
     pub fn set_value(&self, value: &[u8]) -> Result<()> {
         unsafe { RegSetValueExW(self.hkey, self.name, 0, REG_SZ, Some(value)) }
             .ok()