/**
 * A WebGL2 context shared by every chart on the page: browsers allow only a
 * few live contexts (8-16), and dashboards can have more charts than that.
 * Users draw into it and copy the result out before anyone else draws, and
 * set every piece of state they depend on: nothing is reset between users.
 *
 * @ignore
 */
export interface ISharedGL {
    canvas: HTMLCanvasElement;
    gl: WebGL2RenderingContext;
    /**
     * Changes when a lost context is restored: textures and programs made
     * before are gone.
     */
    generation: number;
}
/**
 * The shared context, or `undefined` without WebGL2, with software-only
 * WebGL, or while the context is lost.
 *
 * @ignore
 */
export declare function sharedGL(): ISharedGL | undefined;
/**
 * Counts a user of the shared context in; `releaseGL()` counts it out.
 *
 * @ignore
 */
export declare function retainGL(): void;
/**
 * With no users left, the canvas gives back the memory of the largest
 * drawing made in it. The context stays, for whoever comes next.
 *
 * @ignore
 */
export declare function releaseGL(): void;
/**
 * Compiles and links a program, or `undefined` with a console warning.
 *
 * @ignore
 */
export declare function makeProgram(gl: WebGL2RenderingContext, vertexSource: string, fragmentSource: string): WebGLProgram | undefined;
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