Make a Pixel Speech Bubble
I previously noted how preemption makes lock-free programming harder in userspace .. I thought about causing interrupts by re-affining RT threads, but that seems counterproductive. . modeled on lenses and transducers — MIT; iso- date — Miscellaneous date Don't expect a whole lot of online tutorials, though. Speech balloons are a graphic convention used most commonly in comic books, comics and . Fuzzy thought bubbles do not use tails, and are placed near the character who is thinking. This has Alternatively (especially in online-published comics), colours can be used to provide an additional cue about who is speaking. Nov 16, Remove Watermark from Image · Remove Date Stamp from Photos . The app features over built-in fonts that will make your photos . cool speech bubbles, and superb text formatting features make the Adding text to photos is fun, but it can also be beneficial for online business promotion.
In Western graphic art, labels that reveal what a pictured figure is saying have appeared since at least the 13th century. These were in common European use by the early 16th century. Word balloons also known as "banderoles" began appearing in 18th-century printed broadsides, and political cartoons from the American Revolution including some published by Benjamin Franklin often used them.
Outcault 's Yellow Kid is generally credited as the first American comic strip character. His words initially appeared on his yellow shirt, but word balloons very much like those in use today were added almost immediately, as early as By the start of the 20th century, word balloons were ubiquitous; since that time, few American comic strips and comic books have relied on captions, notably Hal Foster 's Prince Valiant and the early Tarzan comic strip in the s.
Speech bubbles[ edit ] The most common is the speech bubble. It comes in two forms for two circumstances: An in-panel character one who is fully or mostly visible in the panel of the strip of comic that the reader is viewing uses a bubble with a pointer, called a tail, directed towards the speaker. When one character has multiple balloons within a panel, often only the balloon nearest to the speaker's head has a tail, and the others are connected to it in sequence by narrow bands.
This style is often used in Mad Magazinedue to its " call-and-response " dialogue-based humor. An off-panel character the comic book equivalent of being "off screen" has several options, some of them rather unconventional.
The first is a standard speech bubble with a tail pointing toward the speaker's position. The second option, which originated in mangahas the tail pointing into the bubble, instead of out. This tail is still pointing towards the speaker. The third option replaces the tail with a sort of bottleneck that connects with the side of the panel. It can be seen in the works of Marjane Satrapi author of Persepolis.
In American comics, a bubble without a tail means that the speaker is not merely outside the reader's field of view but invisible to the viewpoint characteroften as an unspecified member of a crowd.
- Free Speech Bubble Editor
- Fotophire Editing Toolkit
- Event counts with x86-TSO and futexes
Characters distant in space or time from the scene of the panel can still speak, in squared bubbles without a tail; this usage, equivalent to voice-over in film, is not uncommon in American comics for dramatic contrast. In contrast to captions, the corners of such balloons never coincide with those of the panel; for further distinction they often have a double outline, a different background color, or quotation marks. Thought bubbles[ edit ] Thought bubbles come in two forms: The chain thought bubble is the almost universal symbol for thinking in cartoons.
It consists of a large, cloud -like bubble containing the text of the thought, with a chain of increasingly smaller circular bubbles leading to the character.
Some artists use an elliptical bubble instead of a cloud-shaped one. Often animal characters like Snoopy and Garfield "talk" using thought bubbles. Thought bubbles may also be used in circumstances when a character is gagged or otherwise unable to speak.
Another, less conventional thought bubble has emerged: Used in manga by such artists as Ken Akamatsuthe fuzzy bubble is roughly circular in shape generallybut the edge of the bubble is not a line but a collection of spikes close to each other, creating the impression of fuzziness.
Fuzzy thought bubbles do not use tails, and are placed near the character who is thinking. This has the advantage of reflecting the TV equivalent effect: Writers and artists can refuse to use thought bubbles, expressing the action through spoken dialogue and drawing; they are sometimes seen as an inefficient method of expressing thought because they are attached directly to the head of the thinker, unlike methods such as caption boxes, which can be used both as an expression of thought and narration while existing in an entirely different panel from the character thinking.
However, they are restricted to the current viewpoint character. An example is Alan Moore and David Lloyd 's V for Vendettawherein during one chapter, a monologue expressed in captions serves not only to express the thoughts of a character but also the mood, status and actions of three others. Other forms[ edit ] The shape of a speech balloon can be used to convey further information.
Common ones include the following: Scream bubbles indicate a character is screaming or shouting, usually with a jagged outline or a thicker line which can be colored. Their lettering is usually larger or bolder than normal. Broadcast bubbles also known as radio bubbles may have a jagged tail like the conventional drawing of a lightning flash and either a squared-off or jagged outline.
Letters are sometimes italicised without also being bold. Event counts thus preserve lock-freedom and even wait-freedom! We could, for example, use an event count in a lock-free ring buffer: The solution pattern for adaptive locks relies on tight integration with an OS primitive, e.
The control word, the machine word on which waiters spin, encodes its usual data in our case, a version counteras well as a new flag to denote that there are sleepers waiting to be woken up with an OS syscall.
The OS code for futex wake and wait is identical to what userspace would do with mutexes and condition variables waitqueues. Wakers acquire the futex word for writes, and wake up the waitqueue. The difference is that all of this happens in the kernel, which, unlike userspace, can force the scheduler to be helpful.
This setup is simple enough to fully implement in the kernel, yet general enough to be useful. OS-assisted conditional blocking is straightforward enough to adapt to event counts.
Incrementing the version counter can use a regular atomic increment; we only need to make sure we can tell whether the sleepers flag might have been set before the increment. If the sleepers flag was set, we clear it with an atomic bit resetand wake up any OS thread blocked on the control word. The waiter then sets the sleepers flag with a compare-and-swap: In the latter failure care, or if the CAS succeeded, the flag is now set.
The waiter can then make a syscall to block on the control word, but only if the control word still has the sleepers flag set and contains the same expected old version counter. However, if we go back to the ring buffer example, there is often only one writer per ring.
Enqueueing an item in a single-producer ring buffer incurs no atomic, only a release store: Replacing the write pointer in a single-producer ring buffer with an event count where each increment incurs an atomic operation is far from a no-brainer. Can we do better, when there is only one incrementer? On x86 or any of the zero other architectures with non-atomic read-modify-write instructions and TSOwe can The operation that must really be fast is incrementing the event counter, especially when the sleepers flag is not set.
Setting the sleepers flag on the other hand, may be slower and use atomic instructions, since it only happens when the executing thread is waiting for fresh data. I suggest that we perform the former, the increment on the fast path, with a non-atomic read-modify-write instruction, either inc mem or xadd mem, reg. If the sleepers flag is in the sign bit, we can detect it modulo a false positive on wrap-around in the condition codes computed by inc; otherwise, we must use xadd fetch-and-add and look at the flag bit in the fetched value.
The usual ordering-based arguments are no help in this kind of asymmetric synchronisation pattern. Instead, we must go directly to the xTSO memory model.
The question is then how long waiters must spin before either observing an increment, or knowing that the flag flip will be observed by the next increment. I found an answer by remembering that IRET, the instruction used to return from interrupt handlers, is a full barrier.
Regardless of the bound on store visibility, a waiter can flip the sleepers-are-present flag, spin on the control word for a while, and then start sleeping for short amounts of time e.
However, one second seems reasonable. Even if a core could stall for that long, interrupts fire on every core several times a second, and returning from interrupt handlers acts as a full barrier. No write can remain in the store buffer across interrupts, interrupts that occur at least once per second. It seems safe to assume that, once no activity has been observed on the event count for one second, the sleepers flag will be visible to the next increment.
That assumption is only safe if interrupts do fire at regular intervals. Some latency sensitive systems dedicate cores to specific userspace threads, and move all interrupt processing and preemption away from those cores.
A correctly isolated core running Linux in tickless modewith a single runnable process, might not process interrupts frequently enough. However, this kind of configuration does not happen by accident. I expect that even a half-second stall in such a system would be treated as a system error, and hopefully trigger a watchdog.How To Create Speech Bubbles In Photoshop
Until that time has passed, waiters spin on the control word, then block for short, but growing, amounts of time. Finally, if the control word event count version and sleepers flag has not changed in one second, we assume the incrementer has no write in flight, and will observe the sleepers flag; it is safe to block on the control word forever.
It needs about 30 cycles for an uncontended increment with no waiter, and waking up sleepers adds another cycles on my Exx Linux 4.
Asymmetric flag flip with interrupts on Linux Hazard pointers and epoch reclamation. Two different memory reclamation technique, in which the fundamental complexity stems from nearly identical synchronisation requirements: The hot path is the reader: The diagrams below show all possible interleavings. I simplified the diagrams by not interleaving the first read in step 1: No one implements SC in hardware. Under TSO, reads e.
TSO is so strong that we only have to fix one case, FSSF, where the slow path executes in the middle of the fast path, with the reversal of store and load order allowed by TSO.
Speech balloon - Wikipedia
Simple implementations plug this hole with a store-load barrier between the second and third steps, or implement the store with an atomic read-modify-write instruction that doubles as a barrier. Both modifications are safe and recover SC semantics, but incur a non-negligible overhead the barrier forces the out of order execution engine to flush before accepting more work which is only necessary a minority of the time. The pattern here is similar to the event count, where the slow path signals the fast path that the latter should do something different.
However, where the slow path for event counts wants to wait forever if the fast path never makes progress, hazard pointer and epoch reclamation must detect that case and ignore sleeping threads that are not in the middle of a read-side SMR critical section.
In this kind of asymmetric synchronisation pattern, we wish to move as much of the overhead to the slow cold path. The slow path can execute its write s before making a membarrier syscall. As the next diagram shows, this global barrier lets us rule out the one anomalous execution possible under TSO, without adding any special barrier to the fast path. The problem with membarrier is that it comes in two flavours: The initial, unexpedited, version waits for kernel RCU to run its callback, which, on my machine, takes anywhere between 25 and 50 milliseconds.
For example, if we used the same scheme to nest epoch reclamation ten deep, the outermost reclaimer would be times slower than the innermost one. In reaction to this slowness, potential users of membarrier went back to triggering IPIse. In that expedited mode, each membarrier syscall sends an IPI to every other core Once the hazard pointer slow path has overwritten a pointer, or the epoch slow path advanced the current epoch, we can simply look at the current time, and wait until an interrupt has been handled at a later time on all cores.
The slow path can then scan all the fast path state for evidence that they are still using the overwritten pointer or the previous epoch: What we need is a way to read, for each core, the last time it was definitely processing an interrupt. We can bundle all that logic in a short eBPF program. Whenever the program runs, it gets the current time. That time will go in the thread-local array of interrupt timestamps.