System Brightness Customization

Overview

Introduction

By default, the system brightness of OpenHarmony ranges from 0 to 255 (0 indicates the minimum luminance and 255 the maximum). It is applicable to the entire system and all application windows. Due to hardware restrictions, some display devices are unable to support the system brightness range. To address this issue, OpenHarmony provides the function of customizing the system brightness range. This way, you can adjust the system brightness range based on the hardware specifications of the display devices.

Basic Concepts

System brightness Global brightness of OpenHarmony. The customized brightness range is effective for all application windows.

Window brightness Brightness of an application window. The customized brightness range is effective only for this application window. After a brightness is specified for an application window, its brightness is not affected by the system brightness.

Constraints

The sysparam module of OpenHarmony provides an easy-to-use key-value pair access interface for system services to configure service functions based on their own system parameters. The customization of the system brightness range is dependent on this feature.

How to Develop

Setting Up the Environment

Hardware requirements:

Development board running the standard system, for example, the DAYU200 or Hi3516D V300 open source suite.

Environment requirements:

For details about the requirements on the Linux environment, see Quick Start.

Getting Started with Development

In the target directory, create a target folder by referring to the default brightness value configuration folder. The content is as follows:
```
etc
├── BUILD.gn
├── display.para
├── display.para.dac
```
Write the customized display.para file by referring to the display.para file in the default brightness range configuration folder. Include the customized brightness thresholds, for example, max=150, default=75, and min=50, into the file:
```
# Brightness limits is 0-255.
const.display.brightness.min=50
const.display.brightness.default=75
const.display.brightness.max=150
```
Write the customized display.para.dac file by referring to the display.para.dac file in the default brightness range configuration folder, so as to grant the permission required to access the customized configuration.
```
const.display.brightness.="foundation:foundation:444"
```

Write the customized BUILD.gn file by referring to the BUILD.gn file in the default brightness range configuration folder. Then, put the display.para and display.para.dac files to the /vendor/etc/param directory. For example:

import("//base/powermgr/display_manager/displaymgr.gni")
import("//build/ohos.gni")

## Install display.para to /vendor/etc/param/display.para
ohos_prebuilt_etc("display.para") {
source = "display.para"
relative_install_dir = "param"
install_images = [ chipset_base_dir ]
part_name = "${displaymgr_part_name}"
subsystem_name = "powermgr"
}

ohos_prebuilt_etc("display.para.dac") {
source = "display.para.dac"
relative_install_dir = "param"
install_images = [ chipset_base_dir ]
part_name = "${displaymgr_part_name}"
subsystem_name = "powermgr"
}

group("param_files") {
deps = [
    ":display.para",
    ":display.para.dac",
]
}

Write the customized bundle.json file by referring to the bundle.json file in the default brightness range configuration folder, so as to compile the BUILD.gn file.
```
"service_group": [ "//base/powermgr/display_manager/service/etc:param_files" ]
```
In the preceding code, //base/powermgr/display_manager/service indicates the directory of the created folder, and etc indicates the folder name.
Build the customized version by referring to Quick Start. The following command uses DAYU200 as an example:
```
./build.sh --product-name rk3568 --ccache
```
Burn the customized version to the DAYU200 development board.

Debugging and Verification

After startup, run the following command to launch the shell command line:
```
hdc shell
```
Run the following command to check the console output:
```
hidumper -s 3308 -a -a
```

Check the console output for the customized system brightness thresholds.

The default system brightness thresholds are as follows:

----------------------------------DisplayPowerManagerService---------------------------------
DISPLAY POWER MANAGER DUMP:
Display Id=0 State=2 Discount=1.000000 Brightness=102
DeviceBrightness=102
Support Ambient Light: FALSE
Auto Adjust Brightness: OFF
Brightness Limits: Max=255 Min=5 Default=102

Assume that the system brightness thresholds are set to Max=150 Min=50 Default=75. The console output is as follows:

# cd vendor/etc/param                                                          
# ls
display.para      thermal.para      usb.para.dac  
display.para.dac  thermal.para.dac  
# cat display.para
# Copyright (C) 2022 Huawei Device Co., Ltd.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Brightness limits is 0-255.
const.display.brightness.min=50
const.display.brightness.default=75
const.display.brightness.max=150# 
# 
# cd
# hidumper -s 3308 -a -a

-------------------------------[ability]-------------------------------


----------------------------------DisplayPowerManagerService---------------------------------
DISPLAY POWER MANAGER DUMP:
Display Id=0 State=0 Discount=1.000000 Brightness=75
DeviceBrightness=75
Support Ambient Light: FALSE
Auto Adjust Brightness: OFF
Brightness Limits: Max=150 Min=50 Default=75

Set the system brightness thresholds to the customized values.

Reference

For details about how to write the configuration file during system brightness customization, refer to the default brightness range configuration file.

Default configuration:

# Brightness limits is 0-255.
const.display.brightness.min=5
const.display.brightness.default=102
const.display.brightness.max=255

Packing directory: /system/etc/param