Mirror mode and symmetry

Mirror mode repeats each stroke as its mirror image, or turned round a centre. It is one setting, shared by every drawing tool that takes it, and it stays on from tool to tool until you turn it off. This page covers the modes, the centre, what happens to a glyph in each image, which tools follow it, and its limits.

Tutorial 07, Adding detail, shows each mirror and two radial counts on one stroke, and mirrors the battlements of a castle wall.

Where it is

Item Where Shortcut
Mirror Mode Edit, a tick item Ctrl+M
Mirror X, Mirror Y, Mirror X and Y, Radial Edit > Symmetry none
Symmetry, Folds, Radial centre at The foot of the Tool Options dock, for the tools that take it none
"symmetry" A blockwright-cli replay step (CLI)

Edit > Mirror Mode turns mirror mode on and off, keeping the mode picked. Picking one of the four in Edit > Symmetry picks that mode and turns mirror mode on. The Symmetry list in Tool Options is the same setting: Off turns mirror mode off, and Mirror X, Mirror Y, Mirror X and Y and Radial pick a mode and turn it on. Its tooltip says What every brush repeats a stroke as (mirror mode, Ctrl+M).

Blockwright starts with mirror mode off and the mode set to Mirror X, Folds 4 and no centre. The setting isn't saved when Blockwright closes, or in the project.

The modes

Mode Images of a stroke
Mirror X Two: the stroke and its mirror left to right. Column x comes back at the canvas's width less 1 less x.
Mirror Y Two: the stroke and its mirror top to bottom. Row y comes back at the canvas's height less 1 less y.
Mirror X and Y Four: the stroke, both mirrors, and the half turn.
Radial Folds of them, 2 to 8: the stroke turned a whole turn divided by Folds at a time, round the centre.

The mirrors are always about the middle of the canvas. On a canvas an odd number of cells across, the middle column is its own mirror; on an even one, the axis falls between the two middle columns. Rows work the same way.

Radial turns about the middle of the canvas, or, with Radial centre at ticked, about the cell it names. The turn is made on screen, where a cell is twice as tall as it is wide, and each image is rounded to the nearest cell, so a turned image keeps the shape's look on screen, not its count of cells. A half turn is exact. Tutorial 07 shows 4 and 6 folds; at 8, the corner of upper half blocks along row 2 from column 22 to 27 and left half blocks down column 22 from rows 3 to 5, on a canvas 41 columns by 17 rows:

Eight yellow corners on black round the middle of the canvas, an eighth of a turn apart: the four on the square are clean lines of half blocks, the four on the slant are steps of upper and left half blocks

Images that fall off the canvas are left out; the rest are drawn.

Tool Options

The foot of the Tool Options dock for the Glyph Brush: Glyph, Size 1 with Tip Square, Pressure None, Alpha lock unticked, Symmetry Radial, Folds 4, and Radial centre at ticked with 10 and 6

Option What it does
Symmetry Off, Mirror X, Mirror Y, Mirror X and Y or Radial.
Folds How many images Radial makes, 2 to 8. Its tooltip: Radial: how many turns of the stroke. Greyed out unless Symmetry is Radial.
Radial centre at Ticked, Radial turns about the cell in the two boxes beside it, column then row, instead of the middle of the canvas (tooltip: Turn about this cell instead of the canvas centre). The column runs from 0 to the canvas's width less 1, the row from 0 to its height less 1. Greyed out unless Symmetry is Radial.

When the canvas gets smaller, a centre that is no longer on it moves to the nearest cell that is. The canvas shows no axis or centre: the strokes are the only sign of either.

Four arrows ► laid by the Glyph Brush along row 2 from column 12 to 15, at 4 folds about the cell 10, 6:

Four yellow arrows pointing right at the top, three pointing down to the right of the centre, four pointing left below it, and two pointing up at the far left

The half turn is exact: ◄ along row 10 from column 5 to 8. The quarter turns run down the side, with the arrows turned to ▼ down column 18 from row 7 to 9, and to ▲ down column 2 at rows 4 and 5. Four cells along a row are about two rows tall on screen, and the rounding gives three on one side and two on the other.

What happens to a glyph

Each image is drawn with the glyph turned or flipped to match:

  • A mirror image flips its glyph the way Selection > Flip Horizontally or Flip Vertically does: under Mirror X a ▌ comes back as ▐ and / as \; under Mirror Y a ▀ comes back as ▄. The tables are in What happens to each glyph. A glyph with no mirror, such as a letter, comes back as it is.
  • A quarter turn, at 4 or 8 folds, turns the glyph the way Rotate Clockwise and Rotate Counterclockwise do: ▀ becomes ▐, ► becomes ▼.
  • Any other turn, at 3, 5, 6 or 7 folds and the slanted images at 8, keeps the glyph as it is: CP437 has no half blocks on the slant. The half turn flips both ways.
  • The tip is flipped in a mirror image and kept as it is in a turn, so a round tip stays round.

Which tools follow it

Tools Under mirror mode
Half-Block Brush, Line, Rectangle, Ellipse, Fill Repeat pixels, not cells: a pixel is as tall as it is wide, so every mirror and quarter turn is exact on the pixel grid. Fill floods from the pixel clicked and paints the images of the flooded region.
Glyph Brush, Shade Brush, Frame Repeat cells, with the glyph flipped or turned as above.
Ramp Shade Brush, Colorize Brush, Smudge Brush, Texture Stamp, Glyph Spray Repeat each dab. Under a mirror the texture and the spray read their field folded about the axes, so the images are exact mirrors; a radial image reads the field as it is.
Form Brush, Soft Brush, Despeckle Brush, Outline Brush, Rim Light Brush Each image is worked so that a symmetric canvas stays symmetric: the Form Brush builds a form for each image, and the Outline Brush outlines each image on its own. Under a mirror the Soft Brush shades the images together as mirrors of each other, and the Despeckle and Rim Light brushes work each cell together with its images.
Clone Stamp Each image copies from the image of the source, as it is there, not flipped (The clone stamp).
Ramp Gradient Has no Symmetry: it fills every cell it may paint, so mirror mode has nothing to add.
Select, Move/Transform, Eyedropper, Text Have no Symmetry.
Keyboard and typing with any tool Mirrored under Mirror X only (Typing and pasting).

A selection and Alpha lock clip each image on its own: an image that falls outside the selection is left out where it falls outside.

Typing and pasting

Under Mirror X, typing, Backspace, Delete and a paste of text are repeated in the mirrored column, with each glyph flipped left to right (Keyboard mode). Where an edit and its mirror meet on the same cell, the edit's own wins. /<(▌Ab typed at 1, 1 on a canvas 21 columns wide:

Grey text on black: /<(▌Ab at the left, and its mirror bA▐)>\ at the right

The mirror reads bA▐)>\ from column 14 to 19: the letters keep their shapes, the rest flip. In an IRC or UTF-8 document, a wide character (one that takes two cells) over the centre column can't be mirrored, and the status bar says 1 wide character over the centre column got no mirrored copy (2 wide characters … for more).

Putting a float down, a flip or turn in place and a clear are mirrored under Mirror X too (Selections). Mirror Y, Mirror X and Y and Radial don't repeat typing or any of these.

On a Pixels layer

A Pixels layer takes the pixel tools, and their images land on pixels. A Line from pixel 22, 4 to pixel 34, 10 on a Pixels layer at 5 folds:

Five yellow lines of half-block pixels on black, joined almost end to end into a pentagon round the middle of the canvas

The Glyph Brush and Frame can lay only █, ▀, ▄ and blanks on a Pixels layer. A radial quarter turn turns ▀ and ▄ into ▐ and ▌, which the layer can't hold, so with ▀ or ▄ at 4 or 8 folds the left button paints nothing. The Glyph Brush's status bar says The glyph brush can't paint a Pixels layer: it holds no ▀ turned on its side, which radial symmetry writes; right button erases, and its right button still erases; the Frame says the same with frame for glyph brush, without the last part. Other fold counts keep the glyph, and flips keep █, ▀, ▄ and blanks among themselves, so they paint.

Limits

  • No guide on the canvas. Neither the mirror axis nor the radial centre is drawn.
  • About the canvas. Mirrors are always about the middle of the canvas; only Radial takes a centre of your own.
  • Rounding. A turn other than a half turn is rounded to whole cells, so a line of cells can come back a cell longer or shorter, and a slanted image is a staircase.
  • Mirror X only for typing and selections. The other modes repeat strokes only.
  • Not kept. The setting lasts until Blockwright closes and isn't saved in the project.

Describes Blockwright 0.1.0 (12ee9ef).