dpiWindows10.js

/*
 * DPI support for Windows 10
 *
 * Copyright 2016 Raising the Floor - US
 *
 * Licensed under the New BSD license. You may not use this file except in
 * compliance with this License.
 *
 * You may obtain a copy of the License at
 * https://github.com/GPII/universal/blob/master/LICENSE.txt
 */

"use strict";

/* There is no documented method to change the DPI in Windows 10. The Display Settings applet in Windows calls
 * DisplayConfigSetDeviceInfo with an undocumented structure, which looks like the following:
 *
 * struct DISPLAYCONFIG_SET_DPI {
 *   DISPLAYCONFIG_DEVICE_INFO_HEADER header; // https://msdn.microsoft.com/en-us/library/windows/hardware/ff553920.aspx
 *   INT32 dpiOffset; // see below
 * };
 *
 * The 'type' member of the header, which is used to identify the type of packet, is (uint) -4.
 *
 * The procedure to getting the current DPI is similar. The "official" way of getting it is using
 * GetDeviceCaps(LOGPIXELS[X/Y]), however that appears to only return the DPI that was set at the time of login.
 * The Display Settings applet uses DisplayConfigGetDeviceInfo, and the packet looks something like:
 *
 * struct DISPLAYCONFIG_GET_DPI {
 *   DISPLAYCONFIG_DEVICE_INFO_HEADER header; // https://msdn.microsoft.com/en-us/library/windows/hardware/ff553920.aspx
 *   INT32 minDpiOffset; // The minimum value of dpiOffset.
 *   INT32 dpiOffset;    // see below
 *   INT32 maxDpiOffset; // The maximum value of dpiOffset, determined by the screen resolution.
 * };
 *
 * The 'type' member of header is (uint) -3.
 * maxDpiOffset is the maximum DPI of the current resolution, dpiOffset can be higher but not the actual DPI.
 *
 * The dpiOffset is the number of values away from the display's recommended value, and can be negative. The values
 * (which are a percentage of 96 DPI), are:
 *   [ 100, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500 ]
 * For example, if the recommended DPI is 175%, then a dpiOffset of 0 is 175, 2 is 225, and -1 is 150.
 */

var ref = require("ref");
var Struct = require("ref-struct");
var arrayType = require("ref-array");
var ffi = require("ffi-napi");
var fluid = require("gpii-universal");

var windows = fluid.registerNamespace("gpii.windows");

var t = windows.types;
var c = windows.API_constants;

// These API calls are for only Windows 10
var user32 = ffi.Library("user32", {
    // https://msdn.microsoft.com/en-us/library/windows/hardware/ff553903.aspx
    "DisplayConfigGetDeviceInfo": [
        // DISPLAYCONFIG_DEVICE_INFO_HEADER*
        t.LONG, [ "pointer" ]
    ],
    // https://msdn.microsoft.com/en-us/library/windows/hardware/ff553909.aspx
    "DisplayConfigSetDeviceInfo": [
        // DISPLAYCONFIG_DEVICE_INFO_HEADER*
        t.LONG, [ "pointer" ]
    ],
    // https://msdn.microsoft.com/en-us/library/windows/hardware/ff566772.aspx
    "GetDisplayConfigBufferSizes": [
        t.LONG, [ "uint32", "uint32*", "uint32*" ]
    ],
    // https://msdn.microsoft.com/en-us/library/windows/hardware/ff569215.aspx
    "QueryDisplayConfig":[
        t.LONG,  [ "uint32", "uint32*", "pointer", "uint*", "pointer", "pointer" ]
    ]
});

// sizeof(DISPLAYCONFIG_MODE_INFO)
var DISPLAYCONFIG_MODE_INFO_SIZE = 64;

// THe types of packets send to DisplayConfigGetDeviceInfo/DisplayConfigSetDeviceInfo
// https://msdn.microsoft.com/en-us/library/windows/hardware/ff553924.aspx
var DISPLAYCONFIG_DEVICE_INFO_TYPE = {
    GET_SOURCE_NAME: 1,
    GET_TARGET_NAME: 2,
    GET_TARGET_PREFERRED_MODE: 3,
    GET_ADAPTER_NAME: 4,
    SET_TARGET_PERSISTENCE: 5,
    GET_TARGET_BASE_TYPE: 6,
    GET_SUPPORT_VIRTUAL_RESOLUTION: 7,
    SET_SUPPORT_VIRTUAL_RESOLUTION: 8,
    // undocumented:
    GET_DPI: 0xfffffffd,
    SET_DPI: 0xfffffffc
};

// https://msdn.microsoft.com/en-us/library/dd145066.aspx
windows.MONITORINFOEX = new Struct([
    [t.DWORD, "cbSize"],
    [arrayType(t.LONG, 4), "rcMonitor"],
    [arrayType(t.LONG, 4), "rcWork"],
    [t.DWORD, "dwFlags"],
    [arrayType(t.TCHAR, c.CCHDEVICENAME), "szDevice"]
]);

// https://msdn.microsoft.com/en-us/library/windows/hardware/ff553945.aspx
windows.DISPLAYCONFIG_PATH_INFO = new Struct([
    [t.LUID, "source_adapterId"],
    ["uint32", "source_id"],
    ["uint32", "source_modeInfoIdx"],
    ["uint32", "source_statusFlags"],
    [t.LUID, "target_adapterId"],
    ["uint32", "target_id"],
    ["uint32", "target_modeInfoIdx"],
    ["uint32", "target_outputTechnology"],
    ["uint32", "target_rotation"],
    ["uint32", "target_scaling"],
    ["uint32", "target_refreshRateNumerator"],
    ["uint32", "target_refreshRateDenominator"],
    ["uint32", "target_scanLineOrdering"],
    [t.BOOL, "target_targetAvailable"],
    ["uint32", "target_statusFlags"],
    ["uint32", "flags"]
], { packed: true });

// https://msdn.microsoft.com/en-us/library/windows/hardware/ff553933.aspx
// This structure serves no useful purpose (to GPII), so an anonymous blob of memory is used, instead of defining a
// handful of nested structures.
windows.DISPLAYCONFIG_MODE_INFO = new Struct([
    [arrayType("char", DISPLAYCONFIG_MODE_INFO_SIZE), "reserved"]
]);

// https://msdn.microsoft.com/en-us/library/windows/hardware/ff553920.aspx
windows.DISPLAYCONFIG_DEVICE_INFO_HEADER = new Struct([
    // DISPLAYCONFIG_DEVICE_INFO_TYPE enum
    ["uint32", "type"],
    ["uint32", "size"],
    [t.LUID, "adapterId"],
    ["uint32", "id"]
], { packed: true });

// https://msdn.microsoft.com/en-us/library/windows/hardware/ff553983.aspx
windows.DISPLAYCONFIG_SOURCE_DEVICE_NAME = new Struct([
    [windows.DISPLAYCONFIG_DEVICE_INFO_HEADER, "header"],
    [arrayType(t.TCHAR, c.CCHDEVICENAME), "viewGdiDeviceName"]
]);

// This structure is not documented or defined in the SDK, but it's what control panel appears to use when querying the
// current DPI setting.
windows.DISPLAYCONFIG_GET_DPI = new Struct([
    [windows.DISPLAYCONFIG_DEVICE_INFO_HEADER, "header"],
    ["int32", "minDpiOffset"],
    ["int32", "dpiOffset"],
    ["int32", "maxDpiOffset"]
], {packed: true});

// This structure is not documented or defined in the SDK, but it's what control panel appears to use when adjusting
// the DPI.
windows.DISPLAYCONFIG_SET_DPI = new Struct([
    [windows.DISPLAYCONFIG_DEVICE_INFO_HEADER, "header"],
    ["int32", "dpiOffset"]
]);

/**
 * Create and initialise a new new MONITORINFOEX structure
 * @return {MONITORINFOEX} The structure.
 */
windows.display.createMonitorInfoStruct = function () {
    var obj = new windows.MONITORINFOEX();
    obj.ref().fill(0);
    obj.cbSize = windows.MONITORINFOEX.size;
    return obj;
};

/**
 * Create and initialise a new DISPLAYCONFIG_SOURCE_DEVICE_NAME structure
 * @return {DISPLAYCONFIG_SOURCE_DEVICE_NAME} The structure.
 */
windows.display.createSourceDeviceNameStruct = function () {
    var obj = new windows.DISPLAYCONFIG_SOURCE_DEVICE_NAME();
    obj.ref().fill(0);
    obj.header.size = windows.DISPLAYCONFIG_SOURCE_DEVICE_NAME.size;
    obj.header.type = DISPLAYCONFIG_DEVICE_INFO_TYPE.GET_SOURCE_NAME;
    return obj;
};

/**
 * Create and initialise a new DISPLAYCONFIG_SET_DPI structure
 * @return {DISPLAYCONFIG_SET_DPI} The structure.
 */
windows.display.createSetDpiStruct = function () {
    var obj = new windows.DISPLAYCONFIG_SET_DPI();
    obj.ref().fill(0);
    obj.header.size = windows.DISPLAYCONFIG_SET_DPI.size;
    obj.header.type = DISPLAYCONFIG_DEVICE_INFO_TYPE.SET_DPI;
    return obj;
};

/**
 * Create and initialise a new DISPLAYCONFIG_GET_DPI structure
 * @return {DISPLAYCONFIG_GET_DPI} The structure.
 */
windows.display.createGetDpiStruct = function () {
    var obj = new windows.DISPLAYCONFIG_GET_DPI();
    obj.ref().fill(0);
    obj.header.size = windows.DISPLAYCONFIG_GET_DPI.size;
    obj.header.type = DISPLAYCONFIG_DEVICE_INFO_TYPE.GET_DPI;
    return obj;
};

/**
 * Gets the adapter and monitor (or socket?) id pair of a given device name, by iterating through all display
 * configurations until there's a match.
 * Inspired by https://msdn.microsoft.com/en-us/library/windows/hardware/dn690039.aspx
 *
 * @param {String} deviceName Device name of the display (eg, \\.\DISPLAY1).
 * @return {Object} The adapterId and sourceId of the display.
 */
windows.display.getAdapter = function (deviceName) {
    // Get the array sizes for the configuration
    var pathCountPtr = ref.alloc("uint32");
    var modeInfoCountPtr = ref.alloc("uint32");
    var ret = user32.GetDisplayConfigBufferSizes(c.QDC_ONLY_ACTIVE_PATHS, pathCountPtr, modeInfoCountPtr);
    windows.checkReturnCode(ret);

    var pathCount = pathCountPtr.deref();
    var modeInfoCount = modeInfoCountPtr.deref();

    // Allocate the arrays
    var PathInfoArray = arrayType(windows.DISPLAYCONFIG_PATH_INFO);
    var ModeInfoArray = arrayType(windows.DISPLAYCONFIG_MODE_INFO);
    var pathInfo = new PathInfoArray(pathCount);
    var modeInfo = new ModeInfoArray(modeInfoCount);

    // Get the display configurations
    ret = user32.QueryDisplayConfig(c.QDC_ONLY_ACTIVE_PATHS, pathCountPtr, pathInfo.buffer, modeInfoCountPtr, modeInfo.buffer, ref.NULL);
    windows.checkReturnCode(ret);

    var adapterToGo = null;

    // Find a matching display.
    var sourceName = windows.display.createSourceDeviceNameStruct();
    for (var n = 0; n < pathCount; n++) {
        // Get the device name.
        sourceName.header.adapterId = pathInfo[n].source_adapterId;
        sourceName.header.id = pathInfo[n].source_id;
        ret = user32.DisplayConfigGetDeviceInfo(sourceName.ref());
        if (ret) {
            // There was some problem with this display - ignore it and move on.
            continue;
        }

        var name = windows.fromWideChar(sourceName.viewGdiDeviceName.buffer);
        if (name === deviceName) {
            // There could be more than one matching monitor (a clone). The first one is preferred, but if there's an
            // internal/built-in display later, then let's use that one.
            var isInternal =
                (pathInfo[n].target_outputTechnology === c.DISPLAYCONFIG_OUTPUT_TECHNOLOGY_DISPLAYPORT_EMBEDDED) ||
                (pathInfo[n].target_outputTechnology === c.DISPLAYCONFIG_OUTPUT_TECHNOLOGY_UDI_EMBEDDED) ||
                (pathInfo[n].target_outputTechnology === c.DISPLAYCONFIG_OUTPUT_TECHNOLOGY_INTERNAL);

            if (adapterToGo === null || isInternal) {
                adapterToGo = {
                    adapterId: sourceName.header.adapterId,
                    sourceId: sourceName.header.id
                };
            }
        }
    }

    fluid.log("Display adapter " + deviceName, adapterToGo || "(null)");
    return adapterToGo;
};

/**
 * Gets the device name of the primary monitor. (eg, \\.\DISPLAY1)
 * @return {String} The device name of the primary monitor.
 */
windows.display.getPrimaryMonitorName = function () {
    var monitor = windows.user32.MonitorFromWindow(ref.NULL_POINTER, c.MONITOR_DEFAULTTOPRIMARY);
    var monitorInfo = windows.display.createMonitorInfoStruct();
    windows.user32.GetMonitorInfoW(monitor, monitorInfo.ref());
    return windows.fromWideChar(monitorInfo.szDevice.buffer);
};

/**
 * Sets the DPI scale of the primary display, by specifying the number of values away from an from the recommended
 * setting.
 *
 * @param {Number} offset The offset from the recommended setting.
 * @return {DpiConfig} The newly configured, actual, and minimum/maximum DPI offsets (see getScreenDpi).
 */
windows.display.setScreenDpi = function (offset) {
    // Only change the primary monitor, because that's what setScreenResolution does.
    var monitorName = windows.display.getPrimaryMonitorName();
    var adapter = windows.display.getAdapter(monitorName);

    var setPacket = windows.display.createSetDpiStruct();
    setPacket.header.adapterId = adapter.adapterId;
    setPacket.header.id = adapter.sourceId;

    if (offset < -3) {
        // There isn't a lower limit, so add an artificial bottom cap. If the display supports lower settings then it
        // would probably be unusable beyond this point.
        offset = -3;
    }

    setPacket.dpiOffset = offset;
    var ret = user32.DisplayConfigSetDeviceInfo(setPacket.ref());
    windows.checkReturnCode(ret);

    // Return the new configuration.
    return windows.display.getScreenDpi(adapter);
};

/**
 * Get the configured, maximum, and actual DPI values of the primary display.
 *
 * The value is the number of "notches" away from the recommended setting of the display.
 *
 * The configured scale is what DPI should be if the resolution is high enough, the maximum scale is the highest DPI
 * scale that the current screen resolution supports. The actual scale (what the user is looking at) is the configured
 * scale, capped at the maximum.
 *
 * @param {Object} adapter [optional] The adapter id pair (from getAdapter()).
 * @return {DpiConfig} The newly configured, actual, and minimum/maximum DPI offsets
 */
windows.display.getScreenDpi = function (adapter) {
    if (!adapter) {
        var monitorName = windows.display.getPrimaryMonitorName();
        adapter = windows.display.getAdapter(monitorName);
    }

    var getPacket = windows.display.createGetDpiStruct();
    getPacket.header.adapterId = adapter.adapterId;
    getPacket.header.id = adapter.sourceId;

    var ret = user32.DisplayConfigGetDeviceInfo(getPacket.ref());
    windows.checkReturnCode(ret);

    var configured = getPacket.dpiOffset;
    var maximum = getPacket.maxDpiOffset;
    return {
        configured: configured,
        minimum: getPacket.minDpiOffset,
        maximum: maximum,
        actual: Math.min(configured, maximum)
    };
};

/**
 * DPI Configuration.
 * @typedef {Object} DpiConfig
 * @property {Number} configured The desired DPI setting.
 * @property {Number} minimum The minimum available DPI setting.
 * @property {Number} maximum The maximum available DPI setting.
 * @property {Number} actual The actual DPI setting - the same as configured, but clamped to minimum and maximum.
 */


fluid.defaults("gpii.windows.display.getScreenDpi", {
    gradeNames: "fluid.function",
    argumentMap: {}
});