dwrote 0.4.0

Lightweight binding to DirectWrite.
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/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

use std::slice;
use std::cell::UnsafeCell;
use std::mem::{zeroed, size_of};

use comptr::ComPtr;
use winapi;
use gdi32;
use super::{FontFace, RenderingParams};

#[derive(Debug)]
pub struct BitmapRenderTarget {
    native: UnsafeCell<ComPtr<winapi::IDWriteBitmapRenderTarget>>,
}

impl BitmapRenderTarget {
    pub fn take(native: ComPtr<winapi::IDWriteBitmapRenderTarget>) -> BitmapRenderTarget {
        BitmapRenderTarget {
            native: UnsafeCell::new(native),
        }
    }

    pub unsafe fn as_ptr(&self) -> *mut winapi::IDWriteBitmapRenderTarget {
        (*self.native.get()).as_ptr()
    }

    // A dip is 1/96th of an inch, so this value is the number of pixels per inch divided by 96.
    pub fn set_pixels_per_dip(&self, ppd: f32) {
        unsafe {
            (*self.native.get()).SetPixelsPerDip(ppd);
        }
    }

    pub fn get_memory_dc(&self) -> winapi::HDC {
        unsafe {
            (*self.native.get()).GetMemoryDC()
        }
    }

    pub fn draw_glyph_run(&self,
                          baseline_origin_x: f32,
                          baseline_origin_y: f32,
                          measuring_mode: winapi::DWRITE_MEASURING_MODE,
                          font_face: &FontFace,
                          em_size: f32,
                          glyph_indices: &[u16],
                          glyph_advances: &[f32],
                          glyph_offsets: &[winapi::DWRITE_GLYPH_OFFSET],
                          rendering_params: &RenderingParams,
                          color: &(f32, f32, f32))
        -> winapi::RECT
    {
        unsafe {
            assert!(glyph_indices.len() == glyph_advances.len());
            assert!(glyph_indices.len() == glyph_offsets.len());

            let r = (color.0 * 255.0) as u8;
            let g = (color.1 * 255.0) as u8;
            let b = (color.2 * 255.0) as u8;

            let mut glyph_run: winapi::DWRITE_GLYPH_RUN = zeroed();
            glyph_run.fontFace = font_face.as_ptr();
            glyph_run.fontEmSize = em_size;
            glyph_run.glyphCount = glyph_indices.len() as u32;
            glyph_run.glyphIndices = glyph_indices.as_ptr();
            glyph_run.glyphAdvances = glyph_advances.as_ptr();
            glyph_run.glyphOffsets = glyph_offsets.as_ptr();
            glyph_run.isSideways = 0;
            glyph_run.bidiLevel = 0;

            let mut rect: winapi::RECT = zeroed();
            let hr = (*self.native.get()).DrawGlyphRun(baseline_origin_x,
                                                       baseline_origin_y,
                                                       measuring_mode,
                                                       &glyph_run,
                                                       rendering_params.as_ptr(),
                                                       winapi::RGB(r,g,b),
                                                       &mut rect);
            assert!(hr == 0);
            rect
        }
    }

    // This function expects to have glyphs rendered in WHITE,
    // and pulls out a u8 vector of width*height*4 size with
    // the coverage value (we pull out R) broadcast to the alpha
    // channel, with the color white.  That is, it performs:
    // RGBX -> xxxR, where xxx = 0xff
    pub fn get_opaque_values_as_mask(&self) -> Vec<u8> {
        // Now grossness to pull out the pixels
        unsafe {
            let memory_dc = self.get_memory_dc();
            let mut bitmap: winapi::BITMAP = zeroed();
            let ret = gdi32::GetObjectW(gdi32::GetCurrentObject(memory_dc, winapi::OBJ_BITMAP),
                                        size_of::<winapi::BITMAP>() as i32,
                                        &mut bitmap as *mut _ as *mut winapi::c_void);
            assert!(ret == size_of::<winapi::BITMAP>() as i32);
            assert!(bitmap.bmBitsPixel == 32);

            let width = bitmap.bmWidth as usize;
            let stride = bitmap.bmWidthBytes as usize;
            let height = bitmap.bmHeight as usize;

            let mut out_bytes: Vec<u8> = vec![0; width * height * 4];
            let mut out_u32 = slice::from_raw_parts_mut(out_bytes.as_mut_ptr() as *mut u32,
                                                        width * height);

            for row in 0..height {
                let in_offset = (row * stride) as isize;
                let in_u32 = slice::from_raw_parts(bitmap.bmBits.offset(in_offset) as *const u32,
                                                   width);
                for col in 0..width {
                    let r = in_u32[col] & 0xff;
                    out_u32[width*row + col] = (r << 24) | (0x00ffffffu32);
                }
            }

            out_bytes
        }
    }
}