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Optimize rendering runs of spaces when there is no visual change #4877

Merged
merged 4 commits into from
Mar 13, 2020
Merged

Optimize rendering runs of spaces when there is no visual change #4877

merged 4 commits into from
Mar 13, 2020

Commits on Mar 12, 2020

  1. Optimize rendering runs of spaces when only the foreground changes 

    cmatrix is somewhat of a pathological case for our infrastructure: it
prints out a bunch of green and white characters and then updates them a
million times a second.

It also maintains a column of space between every green character. When
it prints this column, it prints it in "default" or "white". This ends
up making runs of text that look like this:

(def: G=green B=bright white W=white *=matrix char  =space)

G W G W G W G W G W G W G W G W
G W G W G W G W G W G W G W G W
G W G W G W G W G W G W G W G W
G W G W G W G W G W G W G W G W
G W G W G W G W G W G W G W G W
G W G W G W G W G W G W G W G W
G W G W G W G W G W G W G W G W
G W G W G W G W G W G W G W G W

As characters trickle in:

G*W G*W G*W G*W G*W G*W G*W B*W
G*W G*W G*W G*W G*W G*W G*W G W
G*W G*W G*W B*W G*W G*W G*W G W
G*W B*W G*W G W G*W G*W G*W G*W
G*W G W G*W G W G*W B*W G*W G*W
B*W G W G*W G W G*W G W B*W G*W
G W G W G*W G W G*W G W G W B*W
G W G W B*W G W G*W G W G W G W

Every one of those color transitions causes us to break up the run of
text and start rendering it again. This impacts GDI, Direct2D *and*
ConPTY.

The problem is, printing a space doesn't **use** the foreground color!

This commit introduces an optimization. When we're about to break a text
cluster becuase its attributes changed, we make sure that it's not just
filled with spaces and differs only in the foreground parameter.

This lets us optimize both the rendering _and_ the PTY output to look
like this:

G*   *   *   *   *   *   *  B*
G*   *   *   *   *   *   *
G*   *   *  B*   *   *   *
G*  B*   *       *   *   *   *
G*       *       *  B*   *   *
B*       *       *      B*   *
G        *       *          B*
G       B*       *

Text will be printed at best line-by-line and at worst only when the
visible properties of the screen actually change.

This speeds up cmatrix remarkably.
    @DHowett
    DHowett committed Mar 12, 2020
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  2. Take global and local inversion into account

    @DHowett
    DHowett committed Mar 12, 2020
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  3. don't forget grid lines

    @DHowett
    DHowett committed Mar 12, 2020
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  4. okay.

    @DHowett
    DHowett committed Mar 12, 2020
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