Fix broken colors and partial flush for ILI9488 display

[andreilukichoff]

Description

Fixed bugs in native Ili9488 display driver:

• Corrupted colors (incorrect order BGR instead of RGB).
• Corrupted screen when using partial flush.

How Has This Been Tested?

• Tested on LILYGO TTGO T-Relay ESP32 Wireless Module board.
• Colors tested on "Primitives" examples.
• Test application code snippet for Flush (BitBlt) provided.

Screenshots

Left: corrupted colors, Right: fixed

Left: corrupted partial flush, Right: fixed

Types of changes

• Improvement (non-breaking change that improves a feature, code or algorithm)
• Bug fix (non-breaking change which fixes an issue with code or algorithm)
• New feature (non-breaking change which adds functionality to code)
• Breaking change (fix or feature that would cause existing functionality to change)
• Config and build (change in the configuration and build system, has no impact on code or features)
• Dev Containers (changes related with Dev Containers, has no impact on code or features)
• Dependencies/declarations (update dependencies or assembly declarations and changes associated, has no impact on code or features)
• Documentation (changes or updates in the documentation, has no impact on code or features)

Checklist

• My code follows the code style of this project (only if there are changes in source code).
• My changes require an update to the documentation (there are changes that require the docs website to be updated).
• I have updated the documentation accordingly (the changes require an update on the docs in this repo).
• I have read the CONTRIBUTING document.
• I have tested everything locally and all new and existing tests passed (only if there are changes in source code).

BitBlt test app:

using System.Threading;
using System.Device.Gpio;
using nanoFramework.Hardware.Esp32;
using nanoFramework.UI;
using System.Drawing;

namespace nanoFrameworkIli9844DisplayTestApp
{
    public class Program
    {
        const int backLightPin = 32;
        const int chipSelectPin = 15;
        const int dataCommandPin = 2;
        const int resetPin = 4;
        
        static GpioController gpio = new();
        static SpiConfiguration spi = new SpiConfiguration(1, chipSelectPin, dataCommandPin, resetPin, backLightPin);
        static ScreenConfiguration screen = new ScreenConfiguration();

        public static void Main()
        {
            Configuration.SetPinFunction(19, DeviceFunction.SPI1_MISO);
            Configuration.SetPinFunction(23, DeviceFunction.SPI1_MOSI);
            Configuration.SetPinFunction(22, DeviceFunction.SPI1_CLOCK);

            DisplayControl.Initialize(spi, screen, 1024 * 1024);
            
            gpio.OpenPin(backLightPin, PinMode.Output).Write(PinValue.High);

            var buffer = DisplayControl.FullScreen;

            // test full flush
            for (int i = 0; i < 5; i++)
            {
                buffer.DrawRectangle(Color.White, 2, 0, 0, 480, 320, 0, 0,
                    Color.White, 0, 0,
                    Color.Black, 480, 320, Bitmap.OpacityOpaque);
                buffer.Flush();
                Thread.Sleep(500);

                buffer.Clear();
                buffer.Flush();
                Thread.Sleep(500);
            }

            buffer.DrawRectangle(Color.White, 2, 0, 0, 480, 320, 0, 0,
                  Color.White, 0, 0,
                  Color.Black, 480, 320, Bitmap.OpacityOpaque);

            // test partial flush
            for (int i = 0; i < 5; i++)
            {
                buffer.DrawRectangle(Color.White, 2, 100, 100, 200, 200, 0, 0,
                    Color.White, 100, 100,
                    Color.Blue, 300, 300, Bitmap.OpacityOpaque);
                buffer.Flush(100, 100, 200, 200);
                Thread.Sleep(500);

                buffer.DrawRectangle(Color.White, 2, 100, 100, 200, 200, 0, 0,
                 Color.Blue, 100, 100,
                 Color.White, 300, 300, Bitmap.OpacityOpaque);
                buffer.Flush(100, 100, 200, 200);
                Thread.Sleep(500);
            }

            Thread.Sleep(Timeout.Infinite);
        }
    }
}

Summary by CodeRabbit

• Refactor
  • Improved performance and readability of the pixel iteration logic by iterating over x and y coordinates directly, rather than using a single index.
  • Optimized the storage order of color values in the TransferBuffer for better efficiency.

[coderabbitai]

Walkthrough

The changes involve modifying the BitBlt function in the ILI9488_480x320_SPI.cpp file of the nanoFramework Graphics library. The primary updates include altering the loop structure from using a single index to using nested loops over x and y coordinates, calculating the pixel index accordingly. Additionally, the order of storing g and b values in the TransferBuffer has been swapped to optimize memory management and performance.

Changes

File	Change Summary
src/nanoFramework.Graphics/Graphics/Displays/ILI9488_480x320_SPI.cpp	- Modified BitBlt function to use nested loops over x and y coordinates instead of a single index i. Calculated i based on x and y. - Reordered storing of g and b values in TransferBuffer. - Removed numPixels variable. - Adjusted TransferBuffer write operations to new order (r, g, b).

Sequence Diagram(s)

sequenceDiagram
    participant ClientApp
    participant DisplayDriver
    participant TransferBuffer

    ClientApp->>DisplayDriver: Call BitBlt(srcX, srcY, width, height)
    loop For each y from srcY to srcY + height
        loop For each x from srcX to srcX + width
            DisplayDriver->>DisplayDriver: Calculate index i
            DisplayDriver->>TransferBuffer: Store r, g, b values in order
        end
    end
    Note over TransferBuffer: Buffer filled with pixel data
    DisplayDriver-->>ClientApp: BitBlt operation complete

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[andreilukichoff]

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[coderabbitai]

Actionable comments posted: 0

Outside diff range and nitpick comments (1)

src/nanoFramework.Graphics/Graphics/Displays/ILI9488_480x320_SPI.cpp (1)

298-299: Correctness: Ensure proper nesting of loops.

The nested loops should be properly indented for better readability and to avoid confusion.

-    for (uint32_t y = srcY; y < srcY + height; y++)
-    for (uint32_t x = srcX; x < srcX + width; x++)
+    for (uint32_t y = srcY; y < srcY + height; y++) {
+        for (uint32_t x = srcX; x < srcX + width; x++) {

Review details

Configuration used: CodeRabbit UI
Review profile: CHILL

Commits

Files that changed from the base of the PR and between 84cc870 and adac5aa.

Files selected for processing (1)

• src/nanoFramework.Graphics/Graphics/Displays/ILI9488_480x320_SPI.cpp (2 hunks)

Additional comments not posted (2)

src/nanoFramework.Graphics/Graphics/Displays/ILI9488_480x320_SPI.cpp (2)

315-317: LGTM! Ensure correct order of storing color values.

The order of storing r, g, and b values in TransferBuffer looks good. Ensure that this order is consistent with the expected format.

---

301-301: Correctness: Ensure i calculation is accurate.

The index i is calculated based on x and y coordinates. Ensure that Attributes.Width is correctly defined and used.

Verification successful

---

Verification Successful: The calculation of i is accurate.

The index i is correctly calculated based on the x and y coordinates, with Attributes.Width being properly defined and assigned based on the display orientation.

• ILI9488_480x320_SPI.cpp:
  • Lines 173, 179, 185, 191: Attributes.Width is assigned based on the display orientation.
  • Line 301: i calculation uses Attributes.Width.

Scripts executed

The following scripts were executed for the analysis:

Script:

#!/bin/bash
# Description: Verify that `Attributes.Width` is correctly defined and used.

# Test: Search for the definition and usage of `Attributes.Width`. Expect: Proper definition and usage.
rg --type cpp $'Attributes.Width'

Length of output: 9375

---

Script:

#!/bin/bash
# Extract lines from ILI9488_480x320_SPI.cpp where Attributes.Width is defined or assigned values
rg --type cpp --line-number 'Attributes.Width' src/nanoFramework.Graphics/Graphics/Displays/ILI9488_480x320_SPI.cpp

Length of output: 720

---

Script:

#!/bin/bash
# Extract lines around the assignments of Attributes.Width in ILI9488_480x320_SPI.cpp to understand the context
rg --type cpp --context 5 --line-number 'Attributes.Width' src/nanoFramework.Graphics/Graphics/Displays/ILI9488_480x320_SPI.cpp

Length of output: 3361

[Ellerbach]

Thanks for the fix! Looks good all up, you should have a code style PR to merge.

[Ellerbach]

Are you sure about the order? I remember the color order is configurable and depends on the driver.

[andreilukichoff]

The driver only supports SPI and Ili9488 only supports 3-byte color in RGB order in SPI mode. I suppose thats why the order was hardcoded initially.

[alberk8]

Should we expose the RGB and BGR to the managed side so that it can be switched in the hardware which correspond to this in nF .

#define RFLAG_COLOR_RGB       0b00000000     /* RGB */
#define RFLAG_COLOR_BGR       0b00001000     /* BGR */

[andreilukichoff]

If I understand correctly, this flag alters the output signal for panels with different order, while the buffer always uses RGB. If this is the case, we should substitute the hardcoded MADCTL_BGR constant in DisplayDriver::ChangeOrientation with a variable that may be either MADCTL_BGR or 0.

[alberk8]

Can you test it out without flipping the RGB values in code?.

[andreilukichoff]

I just tested it and it works exactly as I expected. It displays incorrect colors with RGB buffer and 0 value instead of MADCTL_BGR, and correct colors with MADCTL_BGR value. And vice versa with BGR buffer.
So my panel utilizes BGR pixels obviously.
I suppose the buffer should always remain RGB since there is no other option mentioned in the datasheet. See page 122.

[alberk8]

Different manufacturer uses different panel with same controller. As far as I know there are two types RGB and BGR.

[andreilukichoff]

Yes and controller uses RGB for buffer and flag to alter signal for different panels. I don't see why buffer should not be RGB in any case.

[alberk8]

May be you want to check with this change and if that is inline with this driver.

[coderabbitai]

Actionable comments posted: 0

Review details

Configuration used: CodeRabbit UI
Review profile: CHILL

Commits

Files that changed from the base of the PR and between adac5aa and 0bae92b.

Files selected for processing (1)

• src/nanoFramework.Graphics/Graphics/Displays/ILI9488_480x320_SPI.cpp (1 hunks)

Files skipped from review as they are similar to previous changes (1)

• src/nanoFramework.Graphics/Graphics/Displays/ILI9488_480x320_SPI.cpp

[josesimoes]

Any further developments on this?