Moving the contents of chrome://gpu Profiling to chrome://tracing.

chrome/browser/resources/gpu_internals/fast_rect_renderer.js

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-
-/**
- * @fileoverview Provides a mechanism for drawing massive numbers of
- * colored rectangles into a canvas in an efficient manner, provided
- * they are drawn left to right with fixed y and height throughout.
- *
- * The basic idea used here is to fuse subpixel rectangles together so that
- * we never issue a canvas fillRect for them. It turns out Javascript can
- * do this quite efficiently, compared to asking Canvas2D to do the same.
- *
- * A few extra things are done by this class in the name of speed:
- * - Viewport culling: off-viewport rectangles are discarded.
- *
- * - The actual discarding operation is done in world space,
- *   e.g. pre-transform.
- *
- * - Rather than expending compute cycles trying to figure out an average
- *   color for fused rectangles from css strings, you instead draw using
- *   palletized colors. The fused rect is the max pallete index encountered.
- *
- * Make sure to flush the trackRenderer before finishing drawing in order
- * to commit any queued drawing operations.
- */
-cr.define('gpu', function() {
-
-  /**
-   * Creates a fast rect renderer with a specific set of culling rules
-   * and color pallette.
-   * @param {GraphicsContext2D} ctx Canvas2D drawing context.
-   * @param {number} vpLeft The leftmost visible part of the drawing viewport.
-   * @param {number} minRectSize Only rectangles with width < minRectSize are
-   *    considered for merging.
-   * @param {number} maxMergeDist Controls how many successive small rectangles
-   *    can be merged together before issuing a rectangle.
-   * @param {number} vpRight The rightmost visible part of the viewport.
-   * @param {Array} pallette The color pallete for drawing. Pallette slots
-   *    should map to valid Canvas fillStyle strings.
-   *
-   * @constructor
-   */
-  function FastRectRenderer(ctx, vpLeft, minRectSize, maxMergeDist, vpRight,
-                            pallette) {
-    this.ctx_ = ctx;
-    this.vpLeft_ = vpLeft;
-    this.minRectSize_ = minRectSize;
-    this.maxMergeDist_ = maxMergeDist;
-    this.vpRight_ = vpRight;
-    this.pallette_ = pallette;
-  }
-
-  FastRectRenderer.prototype = {
-    y_: 0,
-    h_: 0,
-    merging_: false,
-    mergeStartX_: 0,
-    mergeCurRight_: 0,
-
-    /**
-     * Changes the y position and height for subsequent fillRect
-     * calls. x and width are specifieid on the fillRect calls.
-     */
-    setYandH: function(y, h) {
-      this.flush();
-      this.y_ = y;
-      this.h_ = h;
-    },
-
-    /**
-     * Fills rectangle at the specified location, if visible. If the
-     * rectangle is subpixel, it will be merged with adjacent rectangles.
-     * The drawing operation may not take effect until flush is called.
-     * @param {number} colorId The color of this rectangle, as an index
-     *     in the renderer's color pallete.
-     */
-    fillRect: function(x, w, colorId) {
-      var r = x + w;
-      if (r < this.vpLeft_ || x > this.vpRight_) return;
-      if (w < this.minRectSize_) {
-        if (r - this.mergeStartX_ > this.maxMergeDist_)
-          this.flush();
-        if (!this.merging_) {
-          this.merging_ = true;
-          this.mergeStartX_ = x;
-          this.mergeCurRight_ = r;
-          this.mergedColorId = colorId;
-        } else {
-          this.mergeCurRight_ = r;
-          this.mergedColorId = Math.max(this.mergedColorId, colorId);
-        }
-      } else {
-        if (this.merging_)
-          this.flush();
-        this.ctx_.fillStyle = this.pallette_[colorId];
-        this.ctx_.fillRect(x, this.y_, w, this.h_);
-      }
-    },
-
-    /**
-     * Commits any pending fillRect operations to the underlying graphics
-     * context.
-     */
-    flush: function() {
-      if (this.merging_) {
-        this.ctx_.fillStyle = this.pallette_[this.mergedColorId];
-        this.ctx_.fillRect(this.mergeStartX_, this.y_,
-                           this.mergeCurRight_ - this.mergeStartX_, this.h_);
-        this.merging_ = false;
-      }
-    }
-  };
-
-  return {
-    FastRectRenderer: FastRectRenderer
-  };
-
-});