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Let effects declare whether they need source images

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Whether an effect works from the loaded photographs is now part of the
declarative plug-in contract, next to params(): Effect::needsSources()
defaults to true, and blur — which only softens what it is handed — says
no and blurs an empty canvas when given nothing.

Only the first stage of a cascade ever sees the sources, so
chainNeedsSources() just asks the first stage. Both front-ends gate on
that instead of on "are there any images": the CLI only refuses an empty
batch when the chain wants one, and the interface renders a blur-led
chain with no images loaded, saying whichever thing is actually missing.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
Si
2026-09-18 15:49:16 +02:00
co-authored by Claude Opus 5
parent a82fba7886
commit 4739d39a51
10 changed files with 112 additions and 48 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/core/chain.cpp
+5
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@@ -26,6 +26,11 @@ Image renderChain(const std::vector<ChainStage>& stages, const std::vector<Image
return image;
}
bool chainNeedsSources(const std::vector<ChainStage>& stages) {
if (stages.empty() || !stages.front().effect) return false;
return stages.front().effect->needsSources();
}
std::string chainTitle(const std::vector<ChainStage>& stages) {
std::string text;
for (const auto& stage : stages) {
src/core/chain.hpp
+5
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@@ -25,6 +25,11 @@ struct ChainStage {
Image renderChain(const std::vector<ChainStage>& stages, const std::vector<Image>& sources,
int width, int height, Rng& rng);
// Whether the chain has to be given source images. Only the first stage ever
// sees them — every later one works on the stage before it — so this is simply
// whether the first effect declares that it needs them.
bool chainNeedsSources(const std::vector<ChainStage>& stages);
// "Scanlines → Blur", for window titles and status lines.
std::string chainTitle(const std::vector<ChainStage>& stages);
src/core/effect.hpp
+5
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@@ -27,6 +27,11 @@ public:
virtual std::string description() const = 0;
virtual const std::vector<ParamSpec>& params() const = 0;
// Whether the effect builds its image out of the loaded source images.
// Effects that only transform what they are handed (blur) say no, and a
// chain that starts with one of them needs no sources at all.
virtual bool needsSources() const { return true; }
virtual Image render(const std::vector<Image>& sources, int width, int height, Rng& rng,
const ParamValues& values) const = 0;
src/effects/blur.cpp
+9 -9
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@@ -100,7 +100,6 @@ void blurVertical(const Image& src, Image& dst, int radius) {
Image BlurEffect::render(const std::vector<Image>& sources, int width, int height, Rng& rng,
const ParamValues& values) const {
if (sources.empty()) throw EffectError("No source images.");
if (width < 1 || height < 1) throw EffectError("Canvas size must be at least 1x1 pixels.");
const int radius = static_cast<int>(std::max(1L, paramInt(values, "radius", 8)));
@@ -108,15 +107,16 @@ Image BlurEffect::render(const std::vector<Image>& sources, int width, int heigh
const std::string direction = paramChoice(values, "direction", "both");
const bool firstSource = paramBool(values, "first_source", false);
// Every random value is drawn here, before any threading, so that a seed
// always gives the same image.
const std::size_t index = firstSource ? 0 : rng.below(sources.size() - 1);
const Image& src = sources[index];
const int sx = static_cast<int>(rng.inRange(0, std::max(0, src.width() - width)));
const int sy = static_cast<int>(rng.inRange(0, std::max(0, src.height() - height)));
Image canvas(width, height);
fillFromSource(canvas, src, sx, sy);
if (!sources.empty()) {
// Every random value is drawn here, before any threading, so that a
// seed always gives the same image.
const std::size_t index = firstSource ? 0 : rng.below(sources.size() - 1);
const Image& src = sources[index];
const int sx = static_cast<int>(rng.inRange(0, std::max(0, src.width() - width)));
const int sy = static_cast<int>(rng.inRange(0, std::max(0, src.height() - height)));
fillFromSource(canvas, src, sx, sy);
}
Image scratch(width, height);
for (int pass = 0; pass < passes; ++pass) {
src/effects/blur.hpp
+6 -4
View File
@@ -4,17 +4,19 @@
namespace effector {
// Fills the canvas with one of the sources and softens it with a separable box
// blur, repeated a few times to approximate a gaussian.
// Softens its input with a separable box blur, repeated a few times to
// approximate a gaussian. It needs no source images of its own: given none it
// blurs an empty canvas, which is what makes it usable as a pure filter stage.
class BlurEffect : public Effect {
public:
std::string name() const override { return "blur"; }
std::string title() const override { return "Blur"; }
std::string description() const override {
return "Fills the canvas from a randomly chosen source and softens it with a repeated "
"box blur, horizontally, vertically or both.";
return "Softens its input with a repeated box blur, horizontally, vertically or both; "
"with sources loaded it fills the canvas from a randomly chosen one first.";
}
const std::vector<ParamSpec>& params() const override;
bool needsSources() const override { return false; }
Image render(const std::vector<Image>& sources, int width, int height, Rng& rng,
const ParamValues& values) const override;
src/gui/window.cpp
+43 -27
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@@ -57,7 +57,13 @@ EffectorWindow::EffectorWindow(const Options& initial) {
applyInitial(initial);
suspendRender_ = false;
if (!sources_->empty()) startRender();
if (loading_) {
placeholder_.set_text(missingText());
} else if (canRender()) {
startRender();
} else {
showPlaceholder();
}
}
EffectorWindow::~EffectorWindow() {
@@ -569,15 +575,7 @@ void EffectorWindow::removeSource(Gtk::ListBoxRow* row) {
}
});
sourceList_.remove(*row);
if (!sources_->empty()) {
requestRender();
} else {
result_ = Image();
saveButton_.set_sensitive(false);
previewStack_.set_visible_child("placeholder");
status_.set_text("");
}
requestRender();
}
void EffectorWindow::onAddImages() {
@@ -680,14 +678,6 @@ void EffectorWindow::removeStage(int index) {
rebuildChainRows();
buildParamWidgets();
if (stages_.empty()) {
result_ = Image();
saveButton_.set_sensitive(false);
previewStack_.set_visible_child("placeholder");
placeholder_.set_text("Add an effect to start.");
status_.set_text("");
return;
}
requestRender();
}
@@ -794,15 +784,40 @@ void EffectorWindow::onSeedEntered() {
void EffectorWindow::onRecreate() {
seed_ = Rng::randomSeed();
seedEntry_.set_text(std::to_string(seed_));
if (sources_->empty()) {
showError("Add at least one source image first.");
if (!canRender()) {
showError(missingText());
return;
}
requestRender();
}
// Whether the effect chain has everything it needs. Only the first stage is
// ever handed the sources, so an effect that does not want them (blur) renders
// happily with none loaded.
bool EffectorWindow::canRender() const {
if (stages_.empty()) return false;
return !sources_->empty() || !chainNeedsSources(stages_);
}
std::string EffectorWindow::missingText() const {
if (stages_.empty()) return "Add an effect to start.";
return "Add source images to start.";
}
void EffectorWindow::showPlaceholder() {
result_ = Image();
saveButton_.set_sensitive(false);
placeholder_.set_text(missingText());
previewStack_.set_visible_child("placeholder");
status_.set_text("");
}
void EffectorWindow::requestRender() {
if (suspendRender_ || sources_->empty() || stages_.empty()) return;
if (suspendRender_) return;
if (!canRender()) {
showPlaceholder();
return;
}
// Spin buttons fire on every step while they are held down; coalesce those
// into one render instead of queueing a job per tick.
debounce_.disconnect();
@@ -815,7 +830,7 @@ void EffectorWindow::requestRender() {
}
void EffectorWindow::startRender() {
if (sources_->empty() || stages_.empty()) return;
if (!canRender()) return;
if (rendering_) {
staleResult_ = true; // a fresh render follows this one
return;
@@ -893,9 +908,11 @@ void EffectorWindow::onRenderFinished() {
std::ostringstream status;
status.setf(std::ios::fixed);
status.precision(1);
status << chainTitle(stages_) << " · " << result_.width() << "×" << result_.height() << " · "
<< sources_->size() << (sources_->size() == 1 ? " source" : " sources") << " · seed "
<< seed_ << " · " << millis << " ms";
status << chainTitle(stages_) << " · " << result_.width() << "×" << result_.height() << " · ";
if (!sources_->empty()) {
status << sources_->size() << (sources_->size() == 1 ? " source" : " sources") << " · ";
}
status << "seed " << seed_ << " · " << millis << " ms";
status_.set_text(status.str());
}
@@ -970,8 +987,7 @@ void EffectorWindow::applyProject(const Project& project, const std::string& pat
suspendRender_ = false;
if (project.sources.empty()) {
placeholder_.set_text("Add source images to start.");
status_.set_text("");
requestRender(); // a chain that needs no sources still has a picture
} else {
addPaths(project.sources); // renders once the images are decoded
}
src/gui/window.hpp
+3
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@@ -33,6 +33,9 @@ private:
void storeParams(); // widgets -> the selected stage's values
void applyInitial(const Options& initial);
bool canRender() const; // a chain, and sources if the chain needs them
std::string missingText() const; // what is still missing before a render
void showPlaceholder(); // drops the preview and says what is missing
void requestRender(); // coalesced: restarts the short debounce timer
void startRender(); // starts a worker, or marks the result stale
void onAddImages();
src/main.cpp
+1 -1
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@@ -40,7 +40,7 @@ int renderHeadless(const effector::Options& options) {
for (const auto& failure : failures) {
std::cerr << "effector: skipping " << failure.path << ": " << failure.message << "\n";
}
if (sources.empty()) {
if (sources.empty() && effector::chainNeedsSources(stages)) {
std::cerr << "effector: no usable source images\n";
return 2;
}