Avoid updating textures more often than needed

[axeldavy]

---

name: Pull Request
about: Create a pull request to help us improve
title: Avoid updating textures more often than needed
assignees: @hoffstadt

Description:
Currently textures are updated more often than needed, which can slow frame rate.
I found this issue using image series with large textures.

This pull request ensures that dynamic textures and raw textures are only updated when needed.

In addition the linux backend has a small bug that is fixed in this pull request. Indeed the previous PBO content was uploaded to the texture. This could introduce artifacts on a single frame. But since the textures are not updated every frame anymore with the proposed change, this fix is mandatory to prevent staying with the wrong content. The windows and Apple code do not seem to have this issue based on my analysis of the code.

In my use-case, the changes result in a x4 speedup.

Concerning Areas:
The changes are pretty trivial, and should be easy to review.

[chankongus]

Sadly this will break some advanced usecases:

import dearpygui.dearpygui as dpg
import array

SIZE = dict(
    X = 500,
    Y = 500,
)

float_rgba = array.array('f') # sizeof 4
float_rgb = array.array('f') # sizeof 4

for i in range(0, SIZE["X"] * SIZE["Y"]):
    #                  r    g  b    a
    float_rgba.extend((1.0, 0, 1.0, 1.0))
    float_rgb.extend ((1.0, 0, 1.0))


def update_dynamic_texture(sender, app_data, target_color):
    if "pick_float_rgba" == sender:
        for i, val in enumerate(target_color):
            target_color[i] = app_data[i % 4]
    elif "pick_float_rgb" == sender:
        for i, val in enumerate(target_color):
            target_color[i] = app_data[i % 3]

dpg.create_context()

with dpg.texture_registry(show=True):
    dpg.add_raw_texture(width=SIZE["X"], height=SIZE["Y"], default_value=float_rgba, format=dpg.mvFormat_Float_rgba,    tag="float_rgba")
    dpg.add_raw_texture(width=SIZE["X"], height=SIZE["Y"], default_value=float_rgb,  format=dpg.mvFormat_Float_rgb,     tag="float_rgb")

with dpg.window(tag="MAIN",label="???"):
    with dpg.group(horizontal=True):
        dpg.add_image("float_rgba")
        dpg.add_color_picker(
            (255, 0, 255, 255),
            tag="pick_float_rgba",
            label="float_rgba",
            no_side_preview=True,
            alpha_bar=True,
            width=SIZE["X"],
            callback=update_dynamic_texture,
            user_data=float_rgba
        )
        dpg.add_image("float_rgb")
        dpg.add_color_picker(
            (255, 0, 255),
            tag="pick_float_rgb",
            label="float_rgb",
            no_side_preview=True,
            alpha_bar=True,
            width=SIZE["X"],
            callback=update_dynamic_texture,
            user_data=float_rgb
        )
                         
dpg.create_viewport(title='???', width=1000, height=1000)
dpg.setup_dearpygui()
dpg.show_viewport()
dpg.set_primary_window("MAIN", True)
dpg.start_dearpygui()
dpg.destroy_context()

Problem stems from fact that with raw textures the data could be modified directly inside the array and DPG just listens upon it, there's just no trigger that it was modified. :(