Ideas from my Development Setup: Clipboard

content/posts/ideas-from-my-dev-setup-clipboard.md

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+title = "Ideas from my Development Setup: Clipboard"
+date = "2020-10-07"
+author = "Ceda EI"
+tags = ["xorg", "linux", "development"]
+keywords = ["xorg", "linux", "development"]
+description = "Things with clipboards: Implicit copying and swapping"
+showFullContent = false
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+
+
+## Ideas
+
+The clipboard is a basic yet integral part of every environment. Over time, I
+have had quite a few ideas regarding clipboards. I have implemented the
+following ideas currently:
+
+### Clipboard Swap
+
+Inspired by vim's registers, I thought about implementing something similar on
+a system level for Xorg. My current implementation basically swaps the contents
+of the clipboard with another clipboard. Currently, the workflow looks
+something like this.
+
+- Copy text `abc`: Writes `abc` to the main clipboard.
+- Press ``` Ctrl+` ```: Swaps content of hidden clipboard with main clipboard.
+- Copy text `def`: Writes `def` to the main clipboard.
+- Paste with `Ctrl+v`: Pastes text `def` as expected.
+- Press ``` Ctrl+` ```: Swaps content of hidden clipboard with main clipboard.
+- Paste: Pastes text `abc`.
+
+### Implicit Copying
+
+Some time ago, a realization hit me that I practically always select text for
+the sake of copying or cutting it. Cutting is just copying and then deleting
+that text. So everytime I select text, it is for copying it. Due to this, I
+implemented implicit copying where text is copied just by selecting it.  So,
+the workflow for copying is reduced from select, ctrl+c, paste to select, paste
+while the workflow for cutting is same.
+
+## Clipboards in Xorg
+
+In Xorg, clipboards are called selections. Xorg has three selections:
+Primary, Secondary and Clipboard.
+
+- Primary: Whenever text is selected, it is copied into primary selection. You
+  can paste contents of the primary selection by pressing middle mouse button
+  in most applications.
+- Secondary: There is no consensus on what this is supposed to be used for and
+  hence it is used by practically nothing.
+- Clipboard: This is the selection that practically every application interacts
+  with. Ctrl-C and Ctrl-V are commonly bound to writing to this clipboard.
+
+## Implementation
+
+Secondary selection is the perfect selection to swap the contents of Clipboard
+selection with. It is practically never used so nothing will overwrite the
+contents of secondary selection.
+
+Here is the `clip_swap.sh` which I have bound to ``` Ctrl+` ``` in my i3
+config.
+
+```bash
+#!/usr/bin/env bash
+
+x=$(xclip -selection secondary -out)
+xclip -selection clipboard -out | xclip -selection secondary
+echo "$x" | xclip -selection clipboard
+```
+
+For implementing implicit copying, I basically needed a daemon that watched for
+changes in primary selection and copies them over to clipboard selection. Here
+are the contents of `clip_syncd.sh`
+
+```bash
+#!/usr/bin/env bash
+# Daemon to synchronize PRIMARY selection with CLIPBOARD selection
+
+old=""
+while :; do
+	new=$(xclip -selection primary -out) || { sleep 0.5; continue; }
+	if [[ $new != "$old" ]]; then
+		xclip -selection primary -out | xclip -selection clipboard -in
+		old="$new"
+	fi
+	sleep 0.5
+done
+```